Fix warnings when compiling with -DNO_IPV6.

A user pointed out that 'family' was uninitialised in config.c, and
when I tried test-building with -DNO_IPV6 (and the usual -Werror, of
course) some unused variables showed up in uxnet.c too.


git-svn-id: svn://svn.tartarus.org/sgt/putty@10135 cda61777-01e9-0310-a592-d414129be87e