* Remove all occurrences if #ifdef USE_WX_ZOOM and all associated code within
  the #else/#endif block ( old zoom code ).
* Removed the build option for USE_WX_ZOOM from CMakeList.txt and config.h.in.
* Removed all scaling code in base screen object.
* Fixed buffered paint and buffered client DC on Windows.  Buffering works
  properly on Linux and Windows.
* Modified kicad_device_context.h to automatically uses buffering on platforms
  where double buffering is supported natively.
* Remove all of the scaled versions of the drawing functions in gr_basic.cpp
  and any support code.
* Removed all traces of ActiveScreen global variable from eeschema and
  gerbview.
* Renamed Recadre_Trace to RedrawScreen in draw frame object.
* Renamed PostDirtyRect to RefreshDrawingRect in draw panel object.
* Lots of code cleaning an Doxygen comment improvements.