This will mostly ensure that each patch used for composition is only loaded once and automatically unloaded once no longer needed.
So far only for paletted rendering, but the same logic can be used for true color as well.
In ZDoom this would affect everything using a patch that got used in a front sky layer, even if the texture was totally unrelated. It is only owed to the low usability of such patches for other purposes that this hasn't caused problems.
* it's no longer the main texture objects managing the pixel buffer but FSoftwareTexture.
* create proper spans for true color textures. The paletted spans only match if the image does not have any translucent pixels.
* create proper warp textures instead of working off the paletted variants.
As a side effect, caching of pixel buffers for texture composition is temporarily disabled, as it management of texture redirections. These things will be reimplemented once things progress further. The existing methods here had their share of serious issues that should be fixed.
This removes the entire palette switch and all the special checks to ensure that no menu can be drawn over this image.
Instead it gives this texture its special palette in the texture manager so that the proper image is created right away.
I decided against exposing this as an editing feature because it is far too specific to this particular image and the raw page format it uses.
A quick check of /idgames shows no project ever replacing it - especially no ZDoom-based project - so no extended handling is needed to make this work with other texture formats.
