The problem was that the editors called ChoosePixelFormat() instead of
wglChoosePixelFormatARB() - and the normal ChoosePixelFormat() has no
attribute for MSAA, so if MSAA is enabled (by SDL2 which calls the wgl
variant), ChoosePixelFormat() will return an incomaptible format and
the editors don't get a working OpenGL context.
So I wrote a wrapper around ChoosePixelFormat() that calls the wgl variant
if available, and all the necessary plumbing around that.
While at it, removed the unused qwgl*PixelFormat function pointers and
supressed the "inconsistent dll linkage" warnings for the gl stubs
Editor also seems to start, didn't test much further.
Only tested 32bit Windows, I fear the editor code isn't 64bit clean..
I hope I haven't broken anything elsewhere..
Sys_GetScanTable() and MapKey() are only used by the Windows backend
or the Windows-only tools.
Rename to Win_GetScanTable() and move MapKey() as Win_MapKey() to
win_input.cpp.
