d3d12: older Windows SDK headers contain wrong function prototypes

Declare correct function pointers ourselves.

Backport of:
- 98fcf112e7
- 89a4d9ae67

(cherry picked from commit c79e616806)

configure.ac

@@ -3343,17 +3343,7 @@ CheckDIRECTX()
     if test x$enable_directx = xyes; then
         AC_CHECK_HEADER(d3d9.h, have_d3d=yes)
         AC_CHECK_HEADER(d3d11_1.h, have_d3d11=yes)
-        AC_MSG_CHECKING(for d3d12 Windows SDK version)
-        AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
-#include <winsdkver.h>
-#include <sdkddkver.h>
-#include <d3d12.h>
-ID3D12Device1 *device;
-#if WDK_NTDDI_VERSION <= 0x0A000008
-asdf
-#endif
-            ]])], [have_d3d12=yes],[have_d3d12=no])
-        AC_MSG_RESULT($have_d3d12)
+        AC_CHECK_HEADER(d3d12.h, have_d3d12=yes)
         AC_CHECK_HEADER(ddraw.h, have_ddraw=yes)
         AC_CHECK_HEADER(dsound.h, have_dsound=yes)
         AC_CHECK_HEADER(dinput.h, have_dinput=yes)