GTK: Don't create widgets in the ::realize handler
GTK: Don't create widgets in the ::realize handler

Creating a widget may lead to a ::hierarchy-changed signal to be
emitted, which itself may lead a tooltip window to be unrealized.
This is problematic because it can lead to the ::unrealize handler to
be called during the ::realize handler, breaking most of the logic
there assuming the widget was properly realized.

This fixes adding a Scintilla widget inside a GTK2 tooltip.  GTK3
didn't seem to be affected.

Also properly destroy the preedit popup window with the widget.

timonwong/foo_uie_wsh_panel_mod.scintilla,timonwong/foo_uie_wsh_panel_mod.scintilla,timonwong/foo_uie_wsh_panel_mod.scintilla,timonwong/foo_uie_wsh_panel_mod.scintilla,timonwong/foo_uie_wsh_panel_mod.scintilla,timonwong/foo_uie_wsh_panel_mod.scintilla,timonwong/foo_uie_wsh_panel_mod.scintilla,timonwong/foo_uie_wsh_panel_mod.scintilla