Added joyent http_parser library, for use in passive receive sample program.
- First pass at a demo of extracting payloads to files from a passively
  received http response stream.  The new '-c' option to bin/passive
  can be used to add content types to be extracted.  deflate and gzip
  content encodings are supported.

- Factored connection context initialization and teardown code.

- TCP and interface stats display now requires new option '-s'.

- Fixed limit-checking bug in argument processing.