Mark's networking code

As cleaned up by @ediosyncratic using git filter-branch (among other dangerous tools).
Includes several fixups from later in the branch, but I may have missed some.
Compiled locally and passes all unit and acceptance tests.  Let's see how it fares more widely ...

I suspect reviewing the gross diff is easiest, as there are (even after squashing out a few) quite a lot of changes of mind along the way.  Also: 106 commits.
That'll be reindent.pl's fault, or rather the emacs mode (that the perl drives) getting confused.  Its syntax-scan to work out indentation doesn't pay any attention to #if-ery :-(
Will fix, thanks for spotting.