There were a couple of "init_opts()" functions a few more cases
of structure initialization that I somehow missed.

Use an unsigned int for the version and add a helper macro so the
code is simplified (and so the error message is a common string).

This adds an option to refresh the stat cache while generating
status.  It also rips out the GIT_PERF stuff I had an makes use
of the trace API to keep statistics about what happens during diff.

The basic structure of each function is courtesy of arrbee.

In the same vein as the previous commits in this series.

This renames git_vector_free_all to the better git_vector_free_deep
and also contains a couple of memory leak fixes based on valgrind
checks.  The fixes are specifically: failure to free global dir
path variables when not compiled with threading on and failure to
free filters from the filter registry that had not be initialized
fully.

I find this easier to read...