Update rabbitmq-c to 0.4.1.

Changes in 0.4.1:
* Removed distribution-specific packaging.
* Bug fixes

Changes in 0.4.0:
* SSL Support
* Non-blocking amqp_simple_wait_frame()
* Per-channel memory management
* High-level consumer API
* Partial heartbeat support
* Bug fixes

See full changelog:

  https://github.com/alanxz/rabbitmq-c/blob/v0.4.1/ChangeLog.md