* constify argument of in6_addrscope();
* use IN6_IS_ADDR_XXX() macro instead of hardcoded values;
* for multicast addresses just return scope value, the only exception
  is addresses with 0x0F scope value (RFC 4291 p2.7.0);

Obtained from:	Yandex LLC
Sponsored by:	Yandex LLC


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271421 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f