net/rabbitmq: Import patch to make it compatible with Elixir 1.9.0
To be exact, they are two patches:
- one to mark rabbitmq_cli compatible with Elixir 1.9.x
- one to make mix(1) work offline (without accessto Hex.pm) again
Reported by: olgeni@
Reviewed by: olgeni@, dch@
Differential Revision: https://reviews.freebsd.org/D20781