HiresTextures: Support parsing DDS files directly

This leaves DDS textures using DXT1/3/5 compressed in-memory, which can
be passed directly to the backend.

Source/Core/VideoCommon/CMakeLists.txt

@@ -14,6 +14,7 @@ set(SRCS
   GeometryShaderGen.cpp
   GeometryShaderManager.cpp
   HiresTextures.cpp
+  HiresTextures_DDSLoader.cpp
   ImageWrite.cpp
   IndexGenerator.cpp
   LightingShaderGen.cpp