mil1553: test: fix typo
mil1553: fix stupid typo
mil1553: replace pthread mutex by sys V semaphore

pthread mutexes provide only thread-safety, but there might
be concurrency between processes (e.g. diagnostic utilities
like the test program). A binary semaphore is used here,
with SEM_UNDO flag operations so that aborted processes will
not lock access until removal of the semaphore set via ipcrm
or reboot of the host
mil1553: move decode/tdecode to ./test