Add libproc to the build configuration.
Merge branch 'fix-macosx' into macosx-process-info
Wire up lookup of the local process/socket originating the proxied connection.

This uses Mac OS X's libproc to find the first process that owns
a matching socket. Currently, the results are simply logged;
the next step will be exposing this generically via
the NAT engine lookup API.
Log the full process path, rather than the MAXCOMLEN-max process name.
Thread pid lookup support through the NAT API.

This exposes the pid lookup code as a standard attribute
of NAT lookup -- if a matching process cannot be found,
or if pid lookup isn't supported by the NAT backend,
a pid of -1 is returned.

This also adds the local_pid to the pxyconn context; this
will be used to populate log strings.
Add a standard API for fetching process name, uid, and gid.
Implement user and group name lookup.
Plumb user/group/path information through the logging API.
Add support for specifying log paths as a specialized format string.

Format string handling is fully implemented, with the exception of
support for automatically creating missing directories.
Implement automatic creation of parent directories.
Merge branch 'macosx-process-info' into fix-macosx