walk sound fix
math fix
pathing fix
fix portability issue
BattlescapeState::updateExpData() - add indicator for FirstKill made

BattleUnit::damage()
	- attempt fix for hit-from direction.
	- rooks need FirstKill to make Squaddie.

+ const
Merge branch 'master' of https://github.com/SupSuper/OpenXcom into oXc_kL

Conflicts:
	src/Battlescape/Pathfinding.cpp
	src/Engine/Options.cpp
	src/Savegame/Base.cpp
	src/Savegame/Tile.cpp