winsock: add check for sin6_scope_id (use CHECK_MEMBERS)

[Vitaly Lipatov]

On old systems sin6_scopy_id was not exist.
I add a check for it in configure.ac and ifdefs in c file.
Rewrite with AC_CHECK_MEMBERS

Changelog:
add check for sin6_scope_id is exist
-- 
Vitaly Lipatov, ALT Linux Team
Russia, Saint-Petersburg, www.etersoft.ru