Moved all the coordinate system calculation to wxDCBase

  Moved all the coordinate system calculation to wxDCBase
   and thus removed all the duplicated code in all wxDC
   classes.
  Problematic is that wxSVGFileDC and wxPostscriptDC inherit
   from wxDC and therefore include platform specific code
   (also before this change) so I chose to override all
   SetLogicalOrigin() etc. methods in these classes and
   call their wxDCBase methods thereby circumventing the
   platform dependent code.
  I'm afraid the Mac code will require updating, too.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45752 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775