Adding border image to Windowed Fullscreen mode.
dllmain.cpp: Minor cleanups.

- Removed unused headers.

- Marked all internal variables and functions as static.
  Most of these functions aren't exported directly; instead,
  their addresses are written to sonic.exe's .text section.

- DllMain(): Updated the function signature to match MSDN.
  http://msdn.microsoft.com/en-us/library/windows/desktop/ms682583(v=vs.85).aspx
Merge remote-tracking branch 'origin/master' into gsft-refactor

Not as much of a merge as a "trick git into thinking it's merged
but do everything manually because all the paths have changed".

Conflicts:
	SADXModLoader/SADXModLoader.vcxproj
	SADXModLoader/dllmain.cpp
DllMain: Removed SADXDebugOutput("WM_ERASESBKGND\n");

Also, marked bgimg as static.