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.

configure.in

@@ -3098,7 +3098,16 @@ XINPUT_STATE_EX s1;
     fi
 
     AC_CHECK_HEADER(mmdeviceapi.h, have_wasapi=yes)
+    if test x$have_wasapi = xyes; then
+        AC_DEFINE(HAVE_MMDEVICEAPI_H,1,[])
+    fi
     AC_CHECK_HEADER(audioclient.h,,have_wasapi=no)
+    if test x$have_wasapi = xyes; then
+        AC_DEFINE(HAVE_AUDIOCLIENT_H,1,[])
+    fi
+
+    AC_CHECK_HEADER(endpointvolume.h,AC_DEFINE(HAVE_ENDPOINTVOLUME_H,1,[]))
+
     AC_ARG_ENABLE(wasapi,
 AC_HELP_STRING([--enable-wasapi], [use the Windows WASAPI audio driver [[default=yes]]]),
                                 , enable_wasapi=yes)