MINOR: buffer: replace b{i,o}_put* with b_put*

The two variants now do exactly the same (appending at the tail of the
buffer) so let's not keep the distinction between these classes of
functions and have generic ones for this. It's also worth noting that
b{i,o}_putchk() wasn't used at all and was removed.
diff --git a/src/checks.c b/src/checks.c
index e9b5318..d2c4035 100644
--- a/src/checks.c
+++ b/src/checks.c
@@ -1518,7 +1518,7 @@
 	 * its own strings.
 	 */
 	if (check->type && check->type != PR_O2_TCPCHK_CHK && !(check->state & CHK_ST_AGENT)) {
-		bo_putblk(check->bo, s->proxy->check_req, s->proxy->check_len);
+		b_putblk(check->bo, s->proxy->check_req, s->proxy->check_len);
 
 		/* we want to check if this host replies to HTTP or SSLv3 requests
 		 * so we'll send the request, and won't wake the checker up now.
@@ -1530,17 +1530,17 @@
 		}
 		else if ((check->type) == PR_O2_HTTP_CHK) {
 			if (s->proxy->options2 & PR_O2_CHK_SNDST)
-				bo_putblk(check->bo, trash.str, httpchk_build_status_header(s, trash.str, trash.size));
+				b_putblk(check->bo, trash.str, httpchk_build_status_header(s, trash.str, trash.size));
 			/* prevent HTTP keep-alive when "http-check expect" is used */
 			if (s->proxy->options2 & PR_O2_EXP_TYPE)
-				bo_putstr(check->bo, "Connection: close\r\n");
-			bo_putstr(check->bo, "\r\n");
+				b_putstr(check->bo, "Connection: close\r\n");
+			b_putstr(check->bo, "\r\n");
 			*b_tail(check->bo) = '\0'; /* to make gdb output easier to read */
 		}
 	}
 
 	if ((check->type & PR_O2_LB_AGENT_CHK) && check->send_string_len) {
-		bo_putblk(check->bo, check->send_string, check->send_string_len);
+		b_putblk(check->bo, check->send_string, check->send_string_len);
 	}
 
 	/* for tcp-checks, the initial connection setup is handled separately as
@@ -2868,7 +2868,7 @@
 			if (check->current_step->string_len >= b_room(check->bo))
 				continue;
 
-			bo_putblk(check->bo, check->current_step->string, check->current_step->string_len);
+			b_putblk(check->bo, check->current_step->string, check->current_step->string_len);
 			*b_tail(check->bo) = '\0'; /* to make gdb output easier to read */
 
 			/* go to next rule and try to send */