Test code for shared memory message queue facility.

This code is intended as a demonstration of how the dynamic shared
memory and dynamic background worker facilities can be used to establish
a group of coooperating processes which can coordinate their activities
using the shared memory message queue facility.  By itself, the code
does nothing particularly interesting: it simply allows messages to
be passed through a loop of workers and back to the original process.
But it's a useful unit test, in addition to its demonstration value.

contrib/test_shm_mq/test_shm_mq.control

@@ -0,0 +1,4 @@
+comment = 'Test code for shared memory message queues'
+default_version = '1.0'
+module_pathname = '$libdir/test_shm_mq'
+relocatable = true