bell: increase bell rate limit from 1/s to 1/100ms

Right now metacity issues only 1 bell event per second. This is
feels buggy when triggering multiple alarm sounds in a terminal.

This patch simple increases the limit to 1/100ms. 100ms is probably a
good choice since the HIG recommends that all user reaction should
happen within 100ms. With this applied pressing 'Left' in gnome-terminal
feels much more responsive.

https://bugzilla.redhat.com/show_bug.cgi?id=498608

https://bugzilla.gnome.org/show_bug.cgi?id=609585

src/core/display.c

@@ -2589,7 +2589,7 @@ event_callback (XEvent   *event,
 	    {
 	    case XkbBellNotify:
               if (XSERVER_TIME_IS_BEFORE(display->last_bell_time,
-                                         xkb_ev->time - 1000))
+                                         xkb_ev->time - 100))
                 {
                   display->last_bell_time = xkb_ev->time;
                   meta_bell_notify (display, xkb_ev);