Removed some old cruft from wxBitmap, moved wxMotif- and

  Removed some old cruft from wxBitmap, moved wxMotif- and
wxControl-specific functionality (GetXXXPixmap) into a separate
class, and fixed the implementation. Adapted wxStaticBitmap,
wxBitmapButton and wxToolBar to the new situation.
  Various fixes to wxToolBar: Realize does not create buttons
multiple times anymore, use the disabled bitmap as the disabled
bitmap, not as the toggled bitmap for toggle buttons (!),
reposition buttons/controls when a tool is removed/deleted.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@19836 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775