- Introduce TGRectMap helper (tiny) class used 
  in TMap, associating a rectangle area with 
  a split frame

- Introduce a new tooltip-like popup window 
  showing the actual split frame layout and 
  allowing to interact with the subframes via 
  their context menu

- Add a few new methods:
  
  Close(): close the embedded frame
  
  CloseAndCollapse(): close the embedded frame 
  and remove the splitframe (unsplit its parent)
  
  ExtractFrame(): undock the embedded frame
  
  SwallowBack(): dock the embedded frame back 
  to its original location
  
  SwitchToMain(): swap the current embedded 
  frame and the one in the main (first) split 
  frame
  
  SplitHor(): horizontally re-split the frame, 
  keeping the actual embedded frame in any side
  
  SplitVer(): vertically re-split the frame, 
  keeping the actual embedded frame in any side

All these methods are accessible via context menu, 
from the tooltip like popup window and allow to 
dynamically split, unsplit and delete split frames


git-svn-id: http://root.cern.ch/svn/root/trunk@24288 27541ba8-7e3a-0410-8455-c3a389f83636