Update sdl1.2.15 xcode proj

The source code release on MilkyTracker website, AND the MilkyTracker GitHub master branch's XCode SDL 1.2 xcode project was outdated. SDLmain.m was outdated and did not work with my SDL 1.2.15, so I replaced it with the latest SDLmain.m. Works good for the first few minutes, I have played a module successfully. New files had to be added into the project or re-added because they were in new locations. See commits for more details.. I simply decided not to rezip the project.