From Valeriy:

- fix silly bug in TGCamvas dtor.
- add setting focus on button press in TGContainer, TGLBContainer.
  That fixes key handling activation problem under win32.


git-svn-id: http://root.cern.ch/svn/root/trunk@10954 27541ba8-7e3a-0410-8455-c3a389f83636