MINOR: peers: Add "log" directive to "peers" section.

This patch is easy to review: let's call parse_logsrv() function to parse
"log" directive as this is already for other sections for proxies.
This enable us to log incoming TCP connections for the listeners for "peers"
sections.

Update the documentation for "peers" section.
diff --git a/src/cfgparse.c b/src/cfgparse.c
index eaad6c2..2e200e8 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -714,6 +714,17 @@
 		}
 		err_code |= parse_server(file, linenum, args, curpeers->peers_fe, NULL, 0);
 	}
+	else if (strcmp(args[0], "log") == 0) {
+		if (init_peers_frontend(file, linenum, NULL, curpeers) != 0) {
+			err_code |= ERR_ALERT | ERR_ABORT;
+			goto out;
+		}
+		if (!parse_logsrv(args, &curpeers->peers_fe->logsrvs, (kwm == KWM_NO), &errmsg)) {
+			ha_alert("parsing [%s:%d] : %s : %s\n", file, linenum, args[0], errmsg);
+			err_code |= ERR_ALERT | ERR_FATAL;
+			goto out;
+		}
+	}
 	else if (strcmp(args[0], "peers") == 0) { /* new peers section */
 		/* Initialize these static variables when entering a new "peers" section*/
 		bind_line = peer_line = 0;