Quite tricky modification, quite tough problem:

TGView frame (base of TGTextView) has a child window - TGViewFrame.
TGViewFrame is never actually painted (DoRedraw never gets called for this window),
but ... it receives Expose event and delegates it to ... its parent - TGTextView,
and TGTextView, it its DoRedraw (or DrawRegion) .... tries to paint into child window - TGViewFrame.
While this is may be OK for X11 or Window, with Cocoa it's a total mess and disaster - if some view is
to be updated, it does not expect a child to be suddenly rendered in the middle of work.

View is not a window.

I've added some quite risky code to address this problem (text scrolling is still wrong) - only 
"static rendering" for a text view works now.


git-svn-id: http://root.cern.ch/svn/root/trunk@44075 27541ba8-7e3a-0410-8455-c3a389f83636