Take putback events into account

Take putback events into account

* gdk/gdk.c (gdk_events_pending): Take putback events into
  account

* gdk/gdk.c (gdk_event_free): Handle dropdataavaible memory
  allocation correctly. (Incompatible change: client must
  _not_ fre event->data and event->data_type.)

* gdk/gdk.c (gdk_event_translate): Changed DND dragging
  so that we don't ungrab pointer when we reenter window
  to prevent extra Enter/Leave effects which had bad
  effects.
  Changed drag zone handling to not send uncessary
  DragEnter events.
  Fixed EnterNotify/LeaveNotify handling. (Only pay
  attention to events on window, don't specify these
  events to XGrabPointer - that isn't valid, and handle
  reverse the sense of the handling of LeaveNotify.)

* gdk/gdkwindow.c (gdk_window_remove_filter): Free removed
  filter.

* gtk/gtk.defs (GdkFont): gdk_font_free => gdk_font_unref

* gtk/gtkmain.{c,h} (gtk_events_pending): new function - apps
  should use this instead of gdk_events_pending.

* gtk/gtkvbbox.h: Fixed a duplication in the headers.

* gtk/testgtk.c (dnd_drop): Don't free the drop data,
  it belongs to the event.