[ANN] posix_mq 0.6.0 - Rubinius support

[Eric Wong]

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.

* http://bogomips.org/ruby_posix_mq/
* (e-mail address removed)
* git://git.bogomips.org/ruby_posix_mq.git

Changes:

This supports Rubinius 1.2 as well as Ruby 1.9. Ruby 1.8 works except
it will block the entire interpreter for blocking operations. Spurious
errors during GC for POSIX_MQ#to_io users are now avoided.