Fix all resolv warnings and turn on -Werror.

The res_init.c changes bring us a bit closer to upstream too, though
there's still work to be done there. Some of the remaining differences
look like bugs we'd want to fix, so we should definitely try to come
back to that.

Change-Id: I50baa148e967c90d55d711e9904ad54c7d724d4d
6 files changed