Include limits.h for CHAR_MAX

This was needed on stable/10.  Apparently, sys/param.h supplies CHAR_MAX
on head.  Include limits.h anyway, for consistency, and because C says so.

Sponsored by:	Dell EMC

usr.bin/locale/locale.c

@@ -40,6 +40,7 @@
 
 #include <dirent.h>
 #include <err.h>
+#include <limits.h>
 #include <locale.h>
 #include <langinfo.h>
 #include <stdio.h>