configury: fix opal_config_pthreads when -lrt is set

the test program was successful without -pthread if -lrt is used.
-pthread *is* required in order to correctly handle
the pthread_atfork function.
OSHMEM: spml ikrit: add call to mxm_mq_destroy()

Make valgrind happy by calling mxm_mq_destroy() on module
close.
Add yalla to the list of default PMLs
.gitignore: add more test executables to be ignored
Add missing var declarations
If someone specifically asks for knem support and we can't do it, then we really should abort.