Bridges and chasms

Not a huge amount of change recently. Binding keys to console commands now works relatively well, and I've fiddled with the map to allow for chasms (tiles with no floor at all), and with that bridges, spurs and ledges. There are a couple of niggles with it (witness the raised lips
around chasm tiles, also the strange shelf on the pillar) but it's a start.

Bridges and things are implicit at the moment; if a floor tile has chasm spaces flanking it in any direction it's counted as a bridge or ledge tile, with no solid matter holding it up. This does mean an isolated floor tile will in fact be floating in space rather than appearing the top of a supporting pillar, but this is an easy exception case. Generally it works well, and I hope for many dramatic battles over bridges spanning apparently infinite depths. Erm, not that they'll really be infinite of course, the plan is that falling into a chasm will drop you onto a deeper dungeon level with much pain and suffering.

I should really put some more coarse geometry under the terrain to give some impression of depth there... and remove the nasty water level hack... and add water... gah. So much to do.

As an aside I also refactored the terrain mesh generation code, and as a result it's now a lot faster. Not fast enough by a long shot, but it was a nice easy start. Easy apart from the hideous annoying stupid bug that ate my entire lunch break of course, but that's to be expected.