Add a helpful comment to parse_bind_address().  No functional changes.
Add (somewhat incomplete) support for SERVER_TRANSPORT_OPTIONS.

To be sepcific, this still needs to handle unescaping values, and needs unit
tests.  Not sure if it's worth bothering scrubbing the SERVER_TRANSPORT_OPTIONS
when freeing either since the values will be stuck in envp anyway since there is
no supported method of scrubbing that buffer, so I might revert where I do that,
though I will keep the utility function that's part of the library.
Removed a ton of bfromcstr calls by using struct tagbstrings instead.  Also change the xport_option parser to scrub various temporary variables properly.

The btlength macro is kind of dinky, but the warning that's emitted when
blength() is used is really is a false positive.
Cleaned up the server init tests.
Add untested support for unescaping the value portion of SERVER_TRANSPORT_OPTIONS.
Add unit tests for the SERVER_TRANSPORT_OPTIONS stuff.
Added an example for how to query server transport options.