- Add kern_semctl() and use it for Linux, IBCS2, and SVR4 ABIs.
- Don't pass a bufsz pointer to kern_shmctl() for operations that don't
need it.
- Add module dependencies for SYSV IPC modules to IBCS2 and SVR4.
- Use kern_shmctl() in SVR4.
- Use kern_msgctl(), kern_semctl(), and kern_shmctl() in IBCS2.
- Mark linux_ipc(), svr4_sys_shmsys(), and svr4_sys_semsys() MPSAFE.