Kept chipping away at chunk based movement, but the problem is now that
the chunks are updated by alternating, i.e. if the character is moving down,
the y chunk index will be decreased first, then the x, then the y, and so on and
so forth until a seg fault occurs.  I'm sure there's a simple error causing this,
but I can't look at this code any more for a while.

Oh, and moving up immediately causes a segfault.
Merge branch 'master' of https://github.com/schiem/roguelike

Conflicts:
	src/gui/canvas.cpp