src/cmd: Add a repurposed import(4), called `9import', to the ports.

The code is adapted from Plan 9's import(4); this allows us to speak
that protocol. We don't currently support AAN (in the works) or
TLS/SSL.

Thanks to David for help with the man page, testing, and development.

R=0intro, rsc
CC=plan9port.codebot
http://codereview.appspot.com/6458100

CONTRIBUTORS

@@ -5,6 +5,7 @@
 
 Abhishek Kulkarni <adkulkar@umail.iu.edu>
 Albert Lee <trisk@acm.jhu.edu>
+Akshat Kumar <seed@mail.nanosouffle.net>
 André Günther <Andre.G@gmx.de>
 Anthony Martin <ality@pbrane.org>
 Anthony Sorace <a@9srv.net>