Defines starting with `p' in kern

• PANICSTR kern/tty.c:1599
• PF_NOSTOP kern/tty_pty.c:76
• PF_PKT kern/tty_pty.c:73
• PF_REMOTE kern/tty_pty.c:75
• PF_STOPPED kern/tty_pty.c:74
• PF_UCNTL kern/tty_pty.c:77
• PIPSIZ kern/uipc_usrreq.c:309
• PPQ kern/kern_synch.c:204