Posix_mq 2.1.0 - POSIX Message Queues for Ruby

POSIX message queues allow local processes to exchange data in the form
of messages. This API is distinct from that provided by System V
message queues, but provides similar functionality.

Changes: ensure compatibility with future Rubies

  • avoid deprecated rb_thread_blocking_region in Ruby 2.0/2.1
  • prepare for rb_thread_blocking_region removal