I'm fine with putting the release version in a header file, thus
necessitating the need to recompile every file that includes it if it's
changed, simply because it's not supposed to be changed that often.
The SDL_arraysize is necessary because sometimes we'll have subreleases
(e.g. 2.4.1, 2.4.2, 2.4.3), and who knows, maybe we'll get to 2.10
someday.
