[SDL2.0.10] Setting SDL_TIMER_WINDOWS to 0 does not stop inclusion

I tried to disable SDL_TIMER_WINDOWS by setting it to 0 in SDL_config_windows.h

This failed, because in SDL_systimer.c the following is used:


whereas this should be:


…if it is to follow the pattern that e.g. the audio drivers use. Here, the conditional compile is done via #if and not #ifdef.