Change IPv6 support function names to be clearer and more compliant.

Several changes:

1) Change "ink_inet" to "ats_ip".
2) Except for a few test functions, "ats_is_ip", "ats_is_ip4", "ats_is_ip6".
3) Change the current "cmp" and "eq" functions to "cmp_addr" and "eq_addr" to reduce confusion about whether the port is compared as well.