This CL implements a TCP protocol for use with fastboot. Protocol
description is given in fastboot_protocol.txt, some examples of
expected behavior can also be found in tcp_test.cpp.
Usage is:
fastboot -s tcp:<hostname>[:port] <command>
Bug: http://b/26558551
Change-Id: If53a514a534489c617db32c4fea8819949121282
David Pursell