Sanitize pane titles and window and session names more consistently and

strictly, prevents C0 characters and other nonvisible characters causing
problems. Reported (with a different fix) by Chris Monardo in GitHub
issue 4999.

session.c

@@ -231,24 +231,6 @@ session_destroy(struct session *s, int notify, const char *from)
 	session_remove_ref(s, __func__);
 }
 
-/* Sanitize session name. */
-char *
-session_check_name(const char *name)
-{
-	char	*copy, *cp, *new_name;
-
-	if (*name == '\0')
-		return (NULL);
-	copy = xstrdup(name);
-	for (cp = copy; *cp != '\0'; cp++) {
-		if (*cp == ':' || *cp == '.')
-			*cp = '_';
-	}
-	utf8_stravis(&new_name, copy, VIS_OCTAL|VIS_CSTYLE|VIS_TAB|VIS_NL);
-	free(copy);
-	return (new_name);
-}
-
 /* Lock session if it has timed out. */
 static void
 session_lock_timer(__unused int fd, __unused short events, void *arg)