[physfs] Failures loading from some (but not all) zip files with particular filenames

[Andi McClure]

Oops, I should have specified, this was with PhysFS 2.0.2 downloaded
from the website, and I built it as part of Polycode
(http://polycode.org/), which might tweak the CMake a bit but I am
pretty sure not enough to make a difference.