Revert half of r10135, and re-fix properly.

One of my changes in uxnet.c was outside the NO_IPV6 ifdef, and broke
compilation in the normal mode. Revert all changes in that file and
replace with a reference to the 'step' parameter in the no-IPv6
version of the SOCKADDR_FAMILY macro, so that those warnings are
squelched anyway.


git-svn-id: svn://svn.tartarus.org/sgt/putty@10136 cda61777-01e9-0310-a592-d414129be87e