Defines starting with `s' in kern

• SFTRC kern/sys_process.c:81
• SIGPROP kern/kern_sig.c:36
• snd kern/uipc_usrreq.c:148
• SQSIZE kern/kern_synch.c:237
• SSTRC kern/sys_process.c:78
• STK_PARAMS kern/sys_generic.c:367