[Bug 38178] Crash with Heroes VI at very begin

https://bugs.winehq.org/show_bug.cgi?id=38178

--- Comment #43 from Stefan Dösinger  ---
Yeah, good luck implementing them without an equivalent GL functionality.
There's GL_NV_texture_compression_vtc, but it has an incompatible block layout
(4x4x4 blocks instead of 4x4x1). This functionality is optional on Windows, so
games have to deal with it not being available (my older nvidia GPUs don't have
it, not sure about newer ones. Radeon GPUs have it). Not advertising it is
better than trying to emulate it somehow and either unpack the data to
uncompressed RGBA8 or do expensive repacking to make it match
GL_NV_texture_compression_vtc.

It may become an issue for d3d10 though.