[fluxus] optimisations and key input commits

[dave]

Hi all,

A big speedup for (recalc-normals) which is a side effect of me trying
to get shadow casting working - it's so far evaded me, I'm getting
winding order problems on the shadow volume... also thinking of how to
make multipass rendering availible from scheme.

... which was all a bit hard so I started playing with dance mats
instead, and there are some additions for keyboard input:

* (keys-down) returns vector of the ascii values of all keys currently
pressed
* (key-special-pressed id) for cursor keys etc
* (keys-special-down) returns vector of all special keys currently
pressed

Special keys are GLUT's name for things like cursor keys that don't map
to ascii values. (keys-down) and (keys-special-down) are for finding out
what the key code is for buttons on things like dance mats where it's
not entirely obvious :)

cheers,

dave