Get rid of the ugly CMD_CHFLAG macro and use a const string (eg "dDU") in the

command entry structs and a couple of functions to check/set the flags.

cmd-find-window.c

@@ -34,7 +34,7 @@ void	cmd_find_window_callback(void *, int);
 const struct cmd_entry cmd_find_window_entry = {
 	"find-window", "findw",
 	CMD_TARGET_WINDOW_USAGE " match-string",
-	CMD_ARG1, 0,
+	CMD_ARG1, "",
 	cmd_target_init,
 	cmd_target_parse,
 	cmd_find_window_exec,