Moved the SDL version back to SDL_version.h

Added a comment at the top of SDL.h with the current version, for informational purposes

.wikiheaders-options

@@ -5,7 +5,7 @@ wikisubdir =
 readmesubdir = docs
 apiprefixregex = (SDL_|SDLK_)
 mainincludefname = SDL3/SDL.h
-versionfname = include/SDL3/SDL.h
+versionfname = include/SDL3/SDL_version.h
 versionmajorregex = \A\#define\s+SDL_MAJOR_VERSION\s+(\d+)\Z
 versionminorregex = \A\#define\s+SDL_MINOR_VERSION\s+(\d+)\Z
 versionmicroregex = \A\#define\s+SDL_MICRO_VERSION\s+(\d+)\Z