Renamed some functions for clarity and readability:
- dns_dispatch_addresponse() -> dns_dispatch_add()
- dns_dispatch_removeresponse() -> dns_dispatch_done()
The dns_dispatch_cancel() function now calls dns_dispatch_done()
directly, so it is no longer ever necessary to call both functions.
dns_dispatch_cancel() is used to terminate dispatch connections
that are still pending, while dns_dispatch_done() is used when they
are complete.