Add support for reading .wux files

[thp]

The tool "WudCompress" converts .wud files to .wux files, eliminating duplicate sectors: https://gbatemp.net/threads/wii-u-image-wud-compression-tool.397901/

The download contains C source for reading .wux files (as well as .wud files, but that functionality is obviously already in wud2app).

It might be useful to have .wux read support in addition to the wudparts-like read ability that already exists.

[JaceCear]

A workaround for the time being is to just use WudCompress to decompress the WUX into a WUD file again and thereafter use wud2app.