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-copy-buffer.c

@@ -43,7 +43,7 @@ struct cmd_copy_buffer_data {
 const struct cmd_entry cmd_copy_buffer_entry = {
 	"copy-buffer", "copyb",
 	"[-a src-index] [-b dst-index] [-s src-session] [-t dst-session]",
-	0, 0,
+	0, "",
 	cmd_copy_buffer_init,
 	cmd_copy_buffer_parse,
 	cmd_copy_buffer_exec,