Defines starting with `s' in kern

• SFTRC kern/sys_process.c:74
• SIGPROP kern/kern_sig.c:37
• snd kern/uipc_usrreq.c:155
• SQSIZE kern/kern_synch.c:238
• SSTRC kern/sys_process.c:71
• STK_PARAMS kern/sys_generic.c:376
• szsigcode kern/kern_exec.c:73