remove gdiplus patches
The latest quirk I discovered is that plugin/gdiplus/Makefile.am patches source files during compilation. It's not obvious to me why this kind of platform-dependent behavior is not managed with ifdefs or
configure. I think we should undo these gymnastics and either (1) rephrase the source to be platform-independent or (2) manage this with ifdefs, with that being my order of preference as well.