* psxmsgq04/init.c, psxmsgq04/psxmsgq04.scn: Tinker with test to ensure
that it hits both failing to allocate memory for the message queue
name and message buffers.
* psxmsgq04/init.c, psxmsgq04/psxmsgq04.doc, psxmsgq04/psxmsgq04.scn:
Update to handle ENFILE case now that POSIX message queues and
message queue file descriptors are configured separately and this
error is possible.
* Makefile.am, psxmsgq04/init.c, psxmsgq04/psxmsgq04.doc,
psxmsgq04/psxmsgq04.scn: Exercise running out of memory while
allocating the message buffers for a POSIX message queue.