Re-apply megasource-specific changes to SDL's cmakelists file.

Update OpenAL Soft CMakeLists.txt to work with megasource

Update OpenAL Soft CMakeLists.txt to work with megasource

Re-apply megasource-specific changes to SDL's CMakeLists.

- Enable SDL_SHARED and disable SDL_STATIC.

- Set SDL_LINK_DIR in parent scope.

- Use custom install() directive.

- Add target_include_directories.

Potentially fix building love package

Merged in EntranceJew/megasource/update-to-libtheora-1.1.1 (pull requ…

…est love2d#5)

Updated libtheora from 1.1 to 1.1.1, we kept the CMakeLists.txt

Made freetype's CMakeLists.txt work with megasource.

Removed TurboJPEG from the list of libraries (it's not used in any lo…

…ve version anymore.)