6.1.4

CHANGES:

• dns-client-{mirage,lwt}: avoid multiple simultaneous connection attempts
  to the same resolver. Now, before a connection is initiated, a Lwt_condition
  is put into the client state which subsequent resolution requests wait for
  (#285 @hannesm, review by @reynir, reported by @kit-ty-kate in
  roburio/http-client-lwt#8)