Polishing in response to Amos' squid-dev review dated 2014/08/08.

Polishing in response to Amos' squid-dev review dated 2014/08/08.

The PASS value masking code in HttpHeader::packInto() is currently unused
because Squid does not (and cannot) use errorpages for native FTP errors.

It is [still] possible to configure ftp_port with transport=HTTP but it is
not clear what the exact effects of that configuration are, if any.

The ftp_port ftp-track-dirs option no longer accepts on|off values. Off is
still the default. Turn on using a valueless "ftp-track-dirs" option.

Other minor polishing touches.