Revert "(Glide64) Get rid of alt_tex_size hack - only relevant for 3Dfx Voodoo"
Reimplement this - performance hack that is badly needed for Mickey's Speedway
Challenge menu screens
This reverts commit 8970a610bf4a52c249e3b75da8c3e0710a66264b.

Conflicts:
	glide2gl/src/Glide64/glidemain.c
	glide2gl/src/Glide64/rdp.h