Port mini vMac guest OS screen ROM patch.

[rickyzhang82]

• Added Mac SE 24 bit ROM screen patch from mini vMac. The guest OS resolution in System 6 can be defined at an arbitrary combination.
• Mac frame buffer base mapping is moved out from guest RAM. This creates more leg room for the host frame buffer.
• Enable System 6 vscreen support in SDL2. Passed build and test.
• Enable System 6 vscreen support in SDL1. Passed build and test.
• Eanble System 6 vscreen support in XWidnow. Passed build and test.

See my screen cast demo here

Travis is great to catch my first PR. It detected that I haven't patched for SDL1 or XWindow.

See Travis indicated the build is green

I personally tested all 3 combinations and make sure this PR works.

Signed-off-by: Ricky Zhang rickyzhang@gmail.com

[rickyzhang82]

@asvitkine

Thanks for your prompt response. After carefully reviewing in vim, I found what you are after in the comment style. It is too bad that Qt Creator doesn't visualize it properly.

I rejected your request of merging SDL1, SDL2, XWindows setting code. Because there are macro and unique codes in XWindows. But I will think about refactoring the common code between SDL1 and SDL2. There is no fun to write and maintain any duplicate code. Also, I believe there are dead code in SDL2 which requires some cleaning. But it will not be in this PR.