win32: nearly-clean compile with stub platform impl
win32: fix libuv linking issue

i think this may be a mingw bug. oh well.
win32: 64 bit build fixes
win32: create `win` platform
win32: create a window
win32: create a GL context
win32: drawing!
win32: correctly redraw during live resize
win32: handle mouse enter/motion/leave
win32: implement mouse press/release
win32: better WGL extension handling
win32: slightly smoother window resizing
win32: implement rtb_get_modkeys()