Update WARNING message.

Update a WARNING message to give a suggested fix when encountered.

(closes issue #16198)
Reported by: atis
Tested by: atis

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@228896 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/channel.c

@@ -759,7 +759,7 @@ struct ast_channel *ast_channel_alloc(int needqueue, int state, const char *cid_
 
 	if (needqueue) {
 		if (pipe(tmp->alertpipe)) {
-			ast_log(LOG_WARNING, "Channel allocation failed: Can't create alert pipe!\n");
+			ast_log(LOG_WARNING, "Channel allocation failed: Can't create alert pipe! Try increasing max file descriptors with ulimit -n\n");
 alertpipe_failed:
 #ifdef HAVE_DAHDI
 			if (tmp->timingfd > -1)