Integrate c-ares with the runtime

[brson]

c-ares is for async DNS, and until now has been included in libuv. They have recently decoupled libuv and c-ares so we will need to do that work ourselves.

joyent/libuv#518

[graydon]

Strange. I don't get it. Does node still do DNS? Did they just move the binding up a level or something?

[brson]

Yes. Node is responsible for using c-ares now.

[mitsuhiko]

c-ares is too buggy from my experience and it does not use the operating system's dns caches. libuv by default just keeps a background thread for such cases and does the lookup in that one. Unless that implicit thread is a problem I think that's a much more reasonable idea.

[pcwalton]

Closing per @mitsuhiko's comment, reopen if this is still desired.