Cosmetic changes to wxSS::GetScreen:

Cosmetic changes to wxSS::GetScreen:
1) Renamed to GetScreenType (so that the name better describes its function)
2) Changed use of <,>,<=,>= operators together with wxSYS_SCREEN_* so that
   'foo is smaller that bar' is written as 'foo < bar' and not (sic) 'foo > bar'

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@15607 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775