Ai player utility

helper functions for AI: testing if an object is in line of sight (and optionally if it's enabled), if a point is clear, and if an object is within a given angular field of view (optionally specified beyond a stock 45 degrees, as well as optionally checking if the target is enabled)
Better docs, please. I personally would like to ensure that people using the engine can get all the information they need from the generated script docs. Tough, but I think it's a good goal to work for. This provides no documentation on either parameter.

Incidentally, why does `target` default to `0`? Surely that's not useful.