Potentially remove dependency on libcares

[blast007]

The c-ares library is used for making asynchronous DNS lookups. We should investigate if we actually need this library or if we could get by with a simple threaded lookup. Libcurl can use c-ares or a threaded lookup already. Also, as mentioned in #74, c-ares may be the source of a crash when building on newer versions of macOS.

[JMakey]

adns is available in Fedora. Perhaps it would be less troublesome than c-ares.