qmake|SDL: Upgraded to SDL 2.0, added a dep_sdl2.pri
The old SDL configuration still exists so that older branches can be built like before. The config variables use a "SDL2_" as prefix instead of "SDL_", e.g., "SDL2_DIR".
Updating one's config_user.pri is therefore required (SDL_ => SDL2_).
qmake|SDL: Upgraded to SDL 2.0, added a dep_sdl2.pri
The old SDL configuration still exists so that older branches can
be built like before. The config variables use a "SDL2_" as prefix
instead of "SDL_", e.g., "SDL2_DIR".
Updating one's config_user.pri is therefore required (SDL_ => SDL2_).