tty_cmd_raw is only used once, for raw UTF-8 output, so rename it to

tty_cmd_utf8character and eliminate the size argument.

tmux.h

@@ -288,7 +288,7 @@ enum tty_cmd {
 	TTY_INSERTCHARACTER,
 	TTY_INSERTLINE,
 	TTY_LINEFEED,
-	TTY_RAW,
+	TTY_UTF8CHARACTER,
 	TTY_REVERSEINDEX,
 };