Remove a couple of outdated FIXME comments.

I had originally planned to implement a Compose-type key locally in
GTK PuTTY, as I did in Windows PuTTY. But in fact we've done this for
some time by delegating to the GTK IM system, which is a far better
idea anyway. So there's no point any more having the FIXME comment
that mentions Compose keys.

Also, there was a comment worrying about what I was going to do about
double-width characters in Pango, which is long since sorted out.

unix/gtkwin.c

@@ -819,10 +819,6 @@ gint key_event(GtkWidget *widget, GdkEventKey *event, gpointer data)
     }
 
     if (event->type == GDK_KEY_PRESS) {
-	/*
-	 * NYI: Compose key (!!! requires Unicode faff before even trying)
-	 */
-
 	/*
 	 * If Alt has just been pressed, we start potentially
 	 * accumulating an Alt+numberpad code. We do this by
@@ -3095,11 +3091,8 @@ void do_beep(void *frontend, int mode)
 int char_width(Context ctx, int uc)
 {
     /*
-     * Under X, any fixed-width font really _is_ fixed-width.
+     * In this front end, double-width characters are handled using a
-     * Double-width characters will be dealt with using a separate
+     * separate font, so this can safely just return 1 always.
-     * font. For the moment we can simply return 1.
-     * 
-     * FIXME: but is that also true of Pango?
      */
     return 1;
 }