TCP transport again

[Alan DeKok]

  I've just committed patches that enable TCP transport in the server.
It was previously off by default.

  The code is a lot cleaner than the previous attempt, and (not
surprisingly), smaller and easier to understand.

  It should provide all of the functionality of 2.1.7, plus TCP
transport for high load systems.  If anyone has spare cycles to check
the usual edge cases, that would help a lot.

  Alan DeKok.