pw_checkname since the beginning if too strict on GECOS field,

relax it a bit so gecos can be used to store multibytes data.

This was unseen before FreeBSD 10.2 as this validation function was motly unused
since FreeBSD 10.2 the usage of this function has been generalized to improve
validation.

Reported by:	des
MFC after:	1 week

usr.sbin/pw/pw_user.c

@@ -642,7 +642,8 @@ pw_checkname(char *name, int gecos)
 	}
 	if (!reject) {
 		while (*ch) {
-			if (strchr(badchars, *ch) != NULL || *ch < ' ' ||
+			if (strchr(badchars, *ch) != NULL ||
+			    (!gecos && *ch < ' ') ||
 			    *ch == 127) {
 				reject = 1;
 				break;