XWA Upgrade

@Driftwood: Yes, that sounds reasonable too

@Trevor: The fix I did yesterday was "quick-and-dirty" but there's probably a way to bring those shadows back (Maybe by mapping alpha-to-"solid-geometry" in the SSAO shader).

I've got a better fix now. It's essentially mapping the alpha channel to "SSAO solidity":
This way the trees now cast SSAO shadows and I don't need to specify a list of textures anywhere: all alpha-enabled textures should work.

@DTM: Check your PMs and let me know if this version works well.

It's perfect! Thank you, it works!