RESOLV: Add an internal function to read TTL from a DNS packet Related: https://fedorahosted.org/sssd/ticket/1884 Adds an internal resolver function that reads the TTL for SRV records as specified by RFC-2181. Several internal c-ares definitions are used until c-ares contains a function that exposes all this information via a parsing function. Reviewed-by: Pavel Březina <pbrezina@redhat.com>