circular distance pt1: plmove & monmove & rl_dist
circularize light sources, apply diagonal cost adjustment to npc movement
Option added
Merge branch 'mo_betta_headlights' into opt_circledist-wip
Option documented
Merge remote branch 'origin/master' into opt_circledist-wip
Nuked #debug-ifs. Restored lightarc shape. Make lightsource downgrade less cpu intensive squares within huge-assed lava fields
fix build error
avoid use of pow() in distance calculation, speeding them up an order of magnitude (thanks quietus!)
Merge trig based distance option.

Conflicts:
	game.h
	lightmap.cpp
	map.h