New texture reading code (now with Strife support!)

[Quasar]

I've completed a rewrite of EE's texture loader which makes it more structured and apparently a little faster, and as a consequence has enabled Strife texture support (for those not in the know, Rogue for some reason felt the need to remove some of the unused fields in DOOM's TEXTURE1 lump format). These changes are also amenable to adding the ability to load texture lumps additively in the future, like ZDoom is already capable of doing. They should even make text-format texture lumps easier when the time comes for that.

Here are some screenshots of Strife being loaded over DOOM II as a PWAD, just as proof of the new ability (they're rather humorous):

http://doomworld.com/eternity/engine/screenshots/earlystrife

[esselfortium]

This is awesome, for all the reasons you listed. :D