Function conflicts with diff module

Issue Summary

The Diff module has a hook called hook_diff, which allows modules to add functionality to comparisons of two nodes.

The Location module has a function called location_diff, which unfortunately is not an implementation of hook_diff(), but instead is an internal function.

So if you have both Diff and Location turned on, you cannot do a revision diff, because the location_diff function is incompatible with being a hook_diff implementation. I propose changing the name of the location_diff function to either _location_diff() or location_loc_diff() or something like that. It apparently only appears in file location.module, and is only used in 2 places (plus the declaration), so it's not a difficult change to make.

The only thing is, I am not sure if other modules in the Location ecosystem could possibly be depending on it? Nothing in the distro zip for Location 6.x-3.0, or any other contrib modules I happen to have on this web site that exhibited the bug, but who knows about other geo-related modules.

This is a simple change, so I won't submit a formal patch, since I don't know what you would want to change the name to.