the CPP symbol it uses from *_HAVENETINET6* to *_NEEDNETINET6* to better
clarify what's going on with regard to the symbol.

Moved processing of --with-kame to before the in6addr_any check, since
it needs to set LIBS for the check to work.  [related to RT #105, and
previous configure.in revision 1.108.]

in6_pkinfo check only needs AC_TRY_COMPILE, not AC_TRY_LINK.