- major shader rework

* handle brightmaps in the main shader instead of keeping separate instances around.
* added detail and glow layers from Raze.
* fixed material setup which could not guarantee that everything was initialized correctly.
* for warped textures, warp all layers. With this brightmaps finally work on warped textures.

Note: Vulkan reports a "device lost" error with this which still needs to be investigated.

src/common/textures/formats/emptytexture.cpp

@@ -69,6 +69,11 @@ FImageSource *EmptyImage_TryCreate(FileReader & file, int lumpnum)
 	return new FEmptyTexture(lumpnum);
 }
 
+FImageSource* CreateEmptyTexture()
+{
+	return new FEmptyTexture(0);
+}
+
 //==========================================================================
 //
 //