Platform: add DirectX mappings

Add the module definitions for:
- Direct3D v12
- XAudio 2.9
- XInput 1.4

Additionally, add the following, unusable modules:
- DXCore

DXCore requires C++ Support (C++11 or newer to be precise) and is not
yet available until C++ interop can be made to work fully.

Author: compnerd

stdlib/public/Platform/winsdk.modulemap

@@ -153,6 +153,35 @@ module WinSDK [system] {
     }
   }
 
+  module DirectX {
+    module Direct3D12 {
+      header "d3d12.h"
+      export *
+
+      link "d3d12.lib"
+      link "dxgi.lib"
+    }
+
+    module XAudio29 {
+      header "xaudio2.h"
+      header "xaudio2fx.h"
+      export *
+
+      link "xaudio2.lib"
+    }
+
+    // XInput 1.4 (Windows 10, XBox) is newer than the XInput 9.1.0 which was
+    // part of Vista.
+    module XInput14 {
+      header "Xinput.h"
+      export *
+
+      link "xinputuap.lib"
+    }
+
+    link "dxguid.lib"
+  }
+
   // FIXME(compnerd) this is a hack for the HWND typedef for DbgHelp
   module __DirectX {
     header "directmanipulation.h"