Revert main.cpp SDL includes

[jbytheway]

Summary

SUMMARY: None

Purpose of change

Trying to fix MSYS linking error reported here.

Describe the solution

Revert part of 595a7e9. It's not safe for main.cpp to include all SDL headers because they #define WinMain. So switch back to just including SDL_version.h.

Additional context

Untested, because I don't have access to the relevant build environment. @ZhilkinSerg can you check if this fixes the issue?

[ZhilkinSerg]

Yeah, it works both on MSYS and VS.

These headers are required for following code and I guess we can try to put SDL version report to sdl_wrappers.h later:

#ifdef TILES
    SDL_version compiled;
    SDL_VERSION( &compiled );
    DebugLog( D_INFO, DC_ALL ) << "SDL version used during compile is "
                               << static_cast<int>( compiled.major ) << "."
                               << static_cast<int>( compiled.minor ) << "."
                               << static_cast<int>( compiled.patch );

    SDL_version linked;
    SDL_GetVersion( &linked );
    DebugLog( D_INFO, DC_ALL ) << "SDL version used during linking and in runtime is "
                               << static_cast<int>( linked.major ) << "."
                               << static_cast<int>( linked.minor ) << "."
                               << static_cast<int>( linked.patch );
#endif

[jbytheway]

These headers are required for following code and I guess we can try to put SDL version report to sdl_wrappers.h later:

I'd propose: make a new header (or find a suitable existing header -- but it has to be one that doesn't include sdl_wrappers.h) to declare a new function (e.g. report_sdl_version) and call that from main.cpp. The definition of that new function can be in some other file which includes sdl_wrappers.h without polluting main.cpp.