cBoundingBox: Added accessors.
Added cWorld::ForEachEntityInBox()
Exported ForEachEntityInBox() to Lua API.
Debuggers: Added a test code for ForEachEntityInBox().

Currently untested, may not run, may crash.
LuaState: Fixed referenced function pushing.

The references are no longer destroyed by the call.
LuaState: Fixed class value-getting off the stack.
Debuggers: Reviewed and fixed the Pickups and Poof commands.

Now they're confirmed working.
Merge remote-tracking branch 'origin/master' into EntitiesInBox
Fixed compilation after chunk Y removal.
Merge pull request #1375 from mc-server/EntitiesInBox

Implemented ForEachEntityInBox