spdycat, shrpx: TLS SNI enhancements

shrpx:
* Added an option to set the TLS SNI extension between shrpx and the
  origin on the command line

spdycat:
* If the user set an explicit host header ( using --headers ) use that
  name for the TLS SNI extension.
* Added the handshake completion time to the verbose output
* The gettimeofday call in get_time was using the incorrect structure
  ( I believe )
* In update_html_parser it was submitting the request regardless of
  the return value of add_request.

Patch from Stephen Ludin