surface.hpp fails to compile by itself

[GabrielRavier]

How to reproduce:

#include <cpp-sdl2/surface.hpp>

Always reproductible, will fail to compile due to SDL_VERSION_ATLEAST not being defined. Also observable when including cpp-sdl2/renderer.hpp. The temporary workaround I'm using is to #include <SDL_version.h> before including a header that includes cpp-sdl2/surface.hpp (which is probably how this can be fixed in cpp-sdl2/surface.hpp), but this is still a relatively annoying problem.