resolv: Second un-ifdef pass

I noticed a few which should have probably been defined for Linux +
bionic, but weren't: HAS_INET6_STRUCTS, HAVE_SA_LEN, RES_USE_EDNS0,
HAVE_SIN6_SCOPE_ID, and probably more.

Test: test netd_integration_test
Change-Id: I5e2b35f3673193ac6f1bc374568e8591cbba03de