Cast char to u_char before passing to isalnum().

OK nicm@

names.c

@@ -97,7 +97,7 @@ parse_window_name(const char *in)
 
 	if (*name != '\0') {
 		ptr = name + strlen(name) - 1;
-		while (ptr > name && !isalnum(*ptr))
+		while (ptr > name && !isalnum((u_char)*ptr))
 			*ptr-- = '\0';
 	}