configury, cmake: add check for endpointvolume.h :

add HAVE_ENDPOINTVOLUME_H, HAVE_MMDEVICEAPI_H and HAVE_AUDIOCLIENT_H
in SDL_config.h.in, SDL_config.h.cmake, SDL_config_windows.h, and in
SDL_config_winrt.h.

include/SDL_config_windows.h

@@ -82,6 +82,9 @@ typedef unsigned int uintptr_t;
 #define HAVE_DSOUND_H 1
 #define HAVE_DXGI_H 1
 #define HAVE_XINPUT_H 1
+#define HAVE_MMDEVICEAPI_H 1
+#define HAVE_AUDIOCLIENT_H 1
+#define HAVE_ENDPOINTVOLUME_H 1
 
 /* This is disabled by default to avoid C runtime dependencies and manifest requirements */
 #ifdef HAVE_LIBC