Pk3 folders are not textures!

What it says on the tin more or less. PK3 folders themselves are counted as "lumps", and due to how the game loads textures they are accidentally counted as textures when they shouldn't be. I obviously fixed that to not happen now.

This is a "backport" because I was originally making this fix for 2.2, but I thought why not fix it for 2.1 too?