Add libproc to the build configuration.
Merge branch 'macosx-yosemite' into fix-macosx
Merge branch 'specify-custom-gid' into fix-macosx
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.
Merge commit '9204418c806fc85ba04c3650dc4002bd440083ca' into nat_local_pid
Define HAVE_DARWIN_LIBPROC on Darwin.
Remove debugging statement.
Detect presence of Darwin libproc.h
Fix memory leak in libproc lookup code
Merge branch 'issue/53'