add support for HLSL/FX

Add support for DirectX HLSL / FX files. The FX files are
just HLSL files with some additional syntax to set
render-states and define multiple shader stages in one file.

Samples are either written by me, or taken from Chromium.

samples/HLSL/accelerated_surface_win.hlsl

@@ -0,0 +1,27 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// To compile these two shaders:
+// fxc /E pixelMain /T ps_2_0 accelerated_surface_win.hlsl
+// fxc /E vertexMain /T vs_2_0 accelerated_surface_win.hlsl
+//
+// fxc is in the DirectX SDK.
+
+struct Vertex {
+  float4 position : POSITION;
+  float2 texCoord : TEXCOORD0;
+};
+
+texture t;
+sampler s;
+
+// Passes a position and texture coordinate to the pixel shader.
+Vertex vertexMain(Vertex input) {
+  return input;
+};
+
+// Samples a texture at the given texture coordinate and returns the result.
+float4 pixelMain(float2 texCoord : TEXCOORD0) : COLOR0 {
+  return tex2D(s, texCoord);
+};