Also get rid of the kernel/messages subdirectory.

- Separate allocation and uploading of textures.
- Move common code for allocating, uploading and downloading textures
  into separate functions.
- Set the correct format and type for DXT textures.

FILE_GetDeviceInfo needs to be efficient, and IOKit is much too slow
to be used here.

makefiles: List bison dependencies explicitly for parallel makes, since older bisons don't support --defines.