CLEANUP: Compare the return value of `XXXcmp()` functions with zero

According to coding-style.txt it is recommended to use:

`strcmp(a, b) == 0` instead of `!strcmp(a, b)`

So let's do this.

The change was performed by running the following (very long) coccinelle patch
on src/:

    @@
    statement S;
    expression E;
    expression F;
    @@

      if (
    (
    dns_hostname_cmp
    |
    eb_memcmp
    |
    memcmp
    |
    strcasecmp
    |
    strcmp
    |
    strncasecmp
    |
    strncmp
    )
    -  (E, F)
    +  (E, F) != 0
      )
    (
      S
    |
      { ... }
    )

    @@
    statement S;
    expression E;
    expression F;
    @@

      if (
    - !
    (
    dns_hostname_cmp
    |
    eb_memcmp
    |
    memcmp
    |
    strcasecmp
    |
    strcmp
    |
    strncasecmp
    |
    strncmp
    )
    -  (E, F)
    +  (E, F) == 0
      )
    (
      S
    |
      { ... }
    )

    @@
    expression E;
    expression F;
    expression G;
    @@

    (
    G &&
    (
    dns_hostname_cmp
    |
    eb_memcmp
    |
    memcmp
    |
    strcasecmp
    |
    strcmp
    |
    strncasecmp
    |
    strncmp
    )
    -  (E, F)
    +  (E, F) != 0
    )

    @@
    expression E;
    expression F;
    expression G;
    @@

    (
    G ||
    (
    dns_hostname_cmp
    |
    eb_memcmp
    |
    memcmp
    |
    strcasecmp
    |
    strcmp
    |
    strncasecmp
    |
    strncmp
    )
    -  (E, F)
    +  (E, F) != 0
    )

    @@
    expression E;
    expression F;
    expression G;
    @@

    (
    (
    dns_hostname_cmp
    |
    eb_memcmp
    |
    memcmp
    |
    strcasecmp
    |
    strcmp
    |
    strncasecmp
    |
    strncmp
    )
    -  (E, F)
    +  (E, F) != 0
    && G
    )

    @@
    expression E;
    expression F;
    expression G;
    @@

    (
    (
    dns_hostname_cmp
    |
    eb_memcmp
    |
    memcmp
    |
    strcasecmp
    |
    strcmp
    |
    strncasecmp
    |
    strncmp
    )
    -  (E, F)
    +  (E, F) != 0
    || G
    )

    @@
    expression E;
    expression F;
    expression G;
    @@

    (
    G &&
    - !
    (
    dns_hostname_cmp
    |
    eb_memcmp
    |
    memcmp
    |
    strcasecmp
    |
    strcmp
    |
    strncasecmp
    |
    strncmp
    )
    -  (E, F)
    +  (E, F) == 0
    )

    @@
    expression E;
    expression F;
    expression G;
    @@

    (
    G ||
    - !
    (
    dns_hostname_cmp
    |
    eb_memcmp
    |
    memcmp
    |
    strcasecmp
    |
    strcmp
    |
    strncasecmp
    |
    strncmp
    )
    -  (E, F)
    +  (E, F) == 0
    )

    @@
    expression E;
    expression F;
    expression G;
    @@

    (
    - !
    (
    dns_hostname_cmp
    |
    eb_memcmp
    |
    memcmp
    |
    strcasecmp
    |
    strcmp
    |
    strncasecmp
    |
    strncmp
    )
    -  (E, F)
    +  (E, F) == 0
    && G
    )

    @@
    expression E;
    expression F;
    expression G;
    @@

    (
    - !
    (
    dns_hostname_cmp
    |
    eb_memcmp
    |
    memcmp
    |
    strcasecmp
    |
    strcmp
    |
    strncasecmp
    |
    strncmp
    )
    -  (E, F)
    +  (E, F) == 0
    || G
    )

    @@
    expression E;
    expression F;
    expression G;
    @@

    (
    - !
    (
    dns_hostname_cmp
    |
    eb_memcmp
    |
    memcmp
    |
    strcasecmp
    |
    strcmp
    |
    strncasecmp
    |
    strncmp
    )
    -  (E, F)
    +  (E, F) == 0
    )
diff --git a/src/cli.c b/src/cli.c
index 8f6d382..c527e90 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -264,7 +264,7 @@
 	struct bind_conf *bind_conf;
 	struct listener *l;
 
-	if (!strcmp(args[1], "socket")) {
+	if (strcmp(args[1], "socket") == 0) {
 		int cur_arg;
 
 		if (*args[2] == 0) {
@@ -335,7 +335,7 @@
 			global.maxsock++; /* for the listening socket */
 		}
 	}
-	else if (!strcmp(args[1], "timeout")) {
+	else if (strcmp(args[1], "timeout") == 0) {
 		unsigned timeout;
 		const char *res = parse_time_err(args[2], &timeout, TIME_UNIT_MS);
 
@@ -366,7 +366,7 @@
 		}
 		global.stats_fe->timeout.client = MS_TO_TICKS(timeout);
 	}
-	else if (!strcmp(args[1], "maxconn")) {
+	else if (strcmp(args[1], "maxconn") == 0) {
 		int maxconn = atol(args[2]);
 
 		if (maxconn <= 0) {
@@ -382,7 +382,7 @@
 		}
 		global.stats_fe->maxconn = maxconn;
 	}
-	else if (!strcmp(args[1], "bind-process")) {  /* enable the socket only on some processes */
+	else if (strcmp(args[1], "bind-process") == 0) {  /* enable the socket only on some processes */
 		int cur_arg = 2;
 		unsigned long set = 0;
 
@@ -803,7 +803,7 @@
 				 * Its location is not remembered here, this is just to switch
 				 * to a gathering mode.
 				 */
-				if (!strcmp(appctx->chunk->area + appctx->chunk->data - strlen(PAYLOAD_PATTERN), PAYLOAD_PATTERN))
+				if (strcmp(appctx->chunk->area + appctx->chunk->data - strlen(PAYLOAD_PATTERN), PAYLOAD_PATTERN) == 0)
 					appctx->st1 |= APPCTX_CLI_ST1_PAYLOAD;
 				else {
 					/* no payload, the command is complete: parse the request */
@@ -1438,15 +1438,15 @@
 
 static int set_severity_output(int *target, char *argument)
 {
-	if (!strcmp(argument, "none")) {
+	if (strcmp(argument, "none") == 0) {
 		*target = CLI_SEVERITY_NONE;
 		return 1;
 	}
-	else if (!strcmp(argument, "number")) {
+	else if (strcmp(argument, "number") == 0) {
 		*target = CLI_SEVERITY_NUMBER;
 		return 1;
 	}
-	else if (!strcmp(argument, "string")) {
+	else if (strcmp(argument, "string") == 0) {
 		*target = CLI_SEVERITY_STRING;
 		return 1;
 	}
@@ -1480,17 +1480,17 @@
 static int cli_parse_set_lvl(char **args, char *payload, struct appctx *appctx, void *private)
 {
 	/* this will ask the applet to not output a \n after the command */
-	if (!strcmp(args[1], "-"))
+	if (strcmp(args[1], "-") == 0)
 	    appctx->st1 |= APPCTX_CLI_ST1_NOLF;
 
-	if (!strcmp(args[0], "operator")) {
+	if (strcmp(args[0], "operator") == 0) {
 		if (!cli_has_level(appctx, ACCESS_LVL_OPER)) {
 			return 1;
 		}
 		appctx->cli_level &= ~ACCESS_LVL_MASK;
 		appctx->cli_level |= ACCESS_LVL_OPER;
 
-	} else if (!strcmp(args[0], "user")) {
+	} else if (strcmp(args[0], "user") == 0) {
 		if (!cli_has_level(appctx, ACCESS_LVL_USER)) {
 			return 1;
 		}
@@ -1580,7 +1580,7 @@
 		memprintf(err, "'%s' : missing fd type", args[cur_arg]);
 		return ERR_ALERT | ERR_FATAL;
 	}
-	if (!strcmp(args[cur_arg+1], "listeners")) {
+	if (strcmp(args[cur_arg + 1], "listeners") == 0) {
 		conf->level |= ACCESS_FD_LISTENERS;
 	} else {
 		memprintf(err, "'%s' only supports 'listeners' (got '%s')",
@@ -1599,13 +1599,13 @@
 		return ERR_ALERT | ERR_FATAL;
 	}
 
-	if (!strcmp(args[cur_arg+1], "user")) {
+	if (strcmp(args[cur_arg + 1], "user") == 0) {
 		conf->level &= ~ACCESS_LVL_MASK;
 		conf->level |= ACCESS_LVL_USER;
-	} else if (!strcmp(args[cur_arg+1], "operator")) {
+	} else if (strcmp(args[cur_arg + 1], "operator") == 0) {
 		conf->level &= ~ACCESS_LVL_MASK;
 		conf->level |= ACCESS_LVL_OPER;
-	} else if (!strcmp(args[cur_arg+1], "admin")) {
+	} else if (strcmp(args[cur_arg + 1], "admin") == 0) {
 		conf->level &= ~ACCESS_LVL_MASK;
 		conf->level |= ACCESS_LVL_ADMIN;
 	} else {
@@ -1973,15 +1973,15 @@
 		else
 			*next_pid = target_pid;
 		return 1;
-	} else if (!strcmp("prompt", args[0])) {
+	} else if (strcmp("prompt", args[0]) == 0) {
 		s->pcli_flags ^= PCLI_F_PROMPT;
 		return argl; /* return the number of elements in the array */
 
-	} else if (!strcmp("quit", args[0])) {
+	} else if (strcmp("quit", args[0]) == 0) {
 		channel_shutr_now(&s->req);
 		channel_shutw_now(&s->res);
 		return argl; /* return the number of elements in the array */
-	} else if (!strcmp(args[0], "operator")) {
+	} else if (strcmp(args[0], "operator") == 0) {
 		if (!pcli_has_level(s, ACCESS_LVL_OPER)) {
 			memprintf(errmsg, "Permission denied!\n");
 			return -1;
@@ -1990,7 +1990,7 @@
 		s->pcli_flags |= ACCESS_LVL_OPER;
 		return argl;
 
-	} else if (!strcmp(args[0], "user")) {
+	} else if (strcmp(args[0], "user") == 0) {
 		if (!pcli_has_level(s, ACCESS_LVL_USER)) {
 			memprintf(errmsg, "Permission denied!\n");
 			return -1;