DXT5 Needs to be re-implemented on Linux

[JJL772]

For now I've removed ATI Compress from Linux builds and Mingw builds. This was used in the bitmap library. This means that any VTFs compressed with DXT5 (any vtf on pc basically) won't load.
Two options for this:

• Pull in a thirdparty dependency (perhaps a brand new version of ATI compress) just for this
• Write our own DXT5 compression library

The ladder seems like the best because of how lazy I am. Writing a new compression library might be a neat project though.

[CoderSear]

I'm using libsquish for a tool I've developed. It seems to work pretty well and supports most of the BC* formats (which includes DXT1-5), although there's a few gotchas in the compressor when compressing DXT1 regarding alpha, and memory usage when compressing might be less than ideal. It's much more sane to integrate into a project than AMD Compressonator. That being said, Compressonator seems to give the user much more control over compression and decompression, which would probably be ideal for a game engine.

(PS: you said "ladder", did you mean "former"?)

[JJL772]

Yea I meant former. Was tired when I wrote this lol

AMD's Compressonator is weird last time I looked into it. Doesn't come off as a library that's easy to integrate into another project. I'll probably use libsquish then.

Thanks for the suggestion