[WIP] Exposing curl_version_info to ruby, supports_asynch_dns? helper

This is a first step to improve the timeout handling in typhoeus. It exposes curl_version_info and uses it to provide a supports_timeout_ms? helper. *This still needs verification* The benefit over just checking for c-ares in the version string (in addition to using the proper api to query it) is that it should also work for the threaded resolver and other (future) async resolvers.