Compiles under Clang.
Working with coords move.
Remove old xyz Grid interface.
All tests (non-poly) pass with CoW. Perf sucks.
Co-locate refcount and data.
Remove vector from Grid.
Prepare merge.
Merge branch 'master' into cow
Added CoW as a compile-time option, enabled by default.
Add chunks spec to huge_map and any_iterator.
Factor out pather state caches.
Remove file too big for Github.
Update polymorphic API and tests to deal with PatherState.
Work around bugs in VS2013. All tests pass.