tests: add IPC_STAT to ipc tests, workaround limitiations of old kernels

tests: add IPC_STAT to ipc tests, workaround limitiations of old kernels

* tests/ipc_msg.c: Include <errno.h>.
(main): Add a test call with IPC_STAT, handle old kernels MSG_STAT behaviour.
* tests/ipc_sem.c: Include <errno.h>.
(main): Add a test call with IPC_STAT, handle old kernels SEM_STAT behaviour.
* tests/ipc_shm.c: Include <errno.h>.
(main): Add a test call with IPC_STAT, handle old kernels SHM_STAT behaviour.