Converted David Ludwig's D3D11 renderer to C and optimized it.

The D3D11 renderer is now slightly faster than D3D9 on my Windows 8 machine (testsprite2 runs at 3400 FPS vs 3100 FPS)
This will need tweaking to fix the Windows RT build.

--HG--
rename : src/render/direct3d11/SDL_render_d3d11.cpp => src/render/direct3d11/SDL_render_d3d11.c

src/render/SDL_render.c

@@ -47,12 +47,12 @@
 
 #if !SDL_RENDER_DISABLED
 static const SDL_RenderDriver *render_drivers[] = {
-#if SDL_VIDEO_RENDER_D3D
-    &D3D_RenderDriver,
-#endif
 #if SDL_VIDEO_RENDER_D3D11
     &D3D11_RenderDriver,
 #endif
+#if SDL_VIDEO_RENDER_D3D
+    &D3D_RenderDriver,
+#endif
 #if SDL_VIDEO_RENDER_OGL
     &GL_RenderDriver,
 #endif