Merge pull request #33 from FLHerne/master

Create branch for adding new wall graphics
Merge pull request #34 from FLHerne/master

Compatibility with antique numpy. End frozen-release distros!
added walls using new strategy for doing corners, although transparency bug
Merge pull request #35 from FLHerne/master

Fix daft colorkeying bug.
new wall images with roundy corners, edge-sensitivity, fairly pretty
better damage overlays for use with dark terrain
base xcf file for walls, alternative wall for randomness
yet another wall type, fuzzier nonvisibility
initial portal graphic
fixed non-randomness of damage
fix merge conflicts
fix randomness
centred portals