pgrep: Remove >15 warning

As comm length can be longer than 15 characters with newer kernels, it
doesn't make sense to have a warning when you make the match string
longer than this.

As a side-effect, it removes the false-positive you got when you used
long regex matches (see issue #92 )

References:
 commit 2cfdbbe897
 procps-ng/procps#92

pgrep.c

@@ -653,10 +653,6 @@ static struct el * select_procs (int *num)
 	closeproc (ptp);
 	*num = matches;
 
-	if ((!matches) && (!opt_full) && opt_pattern && (strlen(opt_pattern) > 15))
-		xwarnx(_("pattern that searches for process name longer than 15 characters will result in zero matches\n"
-				 "Try `%s -f' option to match against the complete command line."),
-				 program_invocation_short_name);
 	return list;
 }