- I added new example to guitest which demonstrates
   how to use TGFileContainer/TGContainer classes.

   This example along with TestListDir example added previously
   reproduces general functionality of TRootBrowser

- added new simplified constructor to TGLVEntry class

- add new method

TGMenuBar::AddPopup(const TString &s, Int_t padleft, Int_t padright,
                   Int_t padtop, Int_t padbottom)

which also simplifies adding of popup-menus

- mods in TGFSContainer.h which allow to make #include <TGFSContainer.h>
  during ROOT session


git-svn-id: http://root.cern.ch/svn/root/trunk@6863 27541ba8-7e3a-0410-8455-c3a389f83636