Add xBRZ filter (2x,3x,4x)

This commit adds xBRZ filter, based mostly on code from HqMAME with a construct or two from alexey-lysiuk fork (I've learned most of this was already done there only after I've written my little bit).

TBH, I can't say whether xBRZ looks better or worse than its respective hqx, just that it looks different.

I didn't add 5x version, as I wasn't sure about hitting size limits, but doing that would be trivial (extra case in  src/gl/textures/gl_hqresize.cpp and extra option in  wadsrc/static/menudef.z).

Like before, can't really say if MSVC will throw a fit.