Merge branch 'no-doubling-texture-heights-plz' into 'master'

No doubling texture heights plz

If you didn't know, apparently SRB2 was hardcoded to double the height of 64x64 textures created using TX_START/TX_END. This has frustrated some a lot. This branch removes this hack at last (there doesn't appear to be any visual issues resulting from removing it, anyway).

srb2win-nodoubletexheight.exe can be found in my FTP folder.

See merge request !85