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/VideoBackends/OGL/main.cpp

@@ -103,6 +103,7 @@ void VideoBackend::InitBackendInfo()
   g_Config.backend_info.bSupportsPaletteConversion = true;
   g_Config.backend_info.bSupportsClipControl = true;
   g_Config.backend_info.bSupportsDepthClamp = true;
+  g_Config.backend_info.bSupportsST3CTextures = false;
 
   g_Config.backend_info.Adapters.clear();