Obsolete function, do not use.
Use SDL_GetRevision() instead; if SDL was carefully built, it will return a git hash.
Returns zero, always, in modern SDL releases.
When SDL was hosted in a Mercurial repository, and was built carefully, this would return the revision number that the build was created from. This number was not reliable for several reasons, but more importantly, SDL is now hosted in a git repository, which does not offer numbers at all, only hashes. This function only ever returns zero now. Don't use it.
Before SDL 2.0.16, this might have returned an unreliable, but non-zero number.
This function is available since SDL 2.0.0.