Implement local_connect_enable option

Building upon [a patch from issue 28 on Google code](https://code.google.com/p/torsocks/issues/detail?id=28#c7), this implements an option (`local_connect_enable`) in `torsocks.conf`, which allows connections to local addresses.

The option is disabled by default (i.e. local connections are refused), and connections to port 53 are blocked unconditionally (regardless of the value of `local_connect_enable`).

This also includes an updated man page and test output.