Removed SDL_bool in favor of plain bool

We require stdbool.h in the build environment, so we might as well use the plain bool type.

If your environment doesn't have stdbool.h, this simple replacement will suffice:
typedef signed char bool;

src/core/linux/SDL_evdev.c

@@ -164,7 +164,7 @@ static void SDL_EVDEV_UpdateKeyboardMute(void)
     }
 }
 
-SDL_bool SDL_EVDEV_Init(void)
+bool SDL_EVDEV_Init(void)
 {
     if (!_this) {
         _this = (SDL_EVDEV_PrivateData *)SDL_calloc(1, sizeof(*_this));