This diff exposes convenience functions through the pathfinder to find reachable navcells from given positions. This is used in D13 to synchronise short and long-range pathfinder, and in the future might have other uses.
This diff also drastically optimises the MakeGoalReachable function, by using global regions to determine connectivity faster for non-point goals, and generally being less naive.
Global regions, being an additional feature, thus slower, required some further optimisations that were not implemented before. Overall, previous testing as shown this patch as being generally faster than svn (see graphs in the comments).
I can't guarantee it returns exactly the same paths as SVN, but they should be close.