Avoid unused variable warning when APR_HAVE_IPV6 == 0.
Avoid unused variable warning when APR_HAVE_IPV6 == 0.

* subversion/libsvn_ra_svn/client.c (make_connection): Wrap declaration of
    ipv6_supported in #if APR_HAVE_IPV6.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion