Defines starting with `h' in bsd/netccitt

• HDHEADERLN bsd/netccitt/hdlc.h:113
• HDLCPROTO_LAP bsd/netccitt/x25.h:79
• HDLCPROTO_LAPB bsd/netccitt/x25.h:80
• HDLCPROTO_LAPD bsd/netccitt/x25.h:82
• HDLCPROTO_UNSET bsd/netccitt/x25.h:81