Defines starting with `h' in netccitt

• HDHEADERLN netccitt/hdlc.h:96
• HDLC netccitt/ccitt_proto.c:41
• HDLCPROTO_LAP netccitt/x25.h:57
• HDLCPROTO_LAPB netccitt/x25.h:58
• HDLCPROTO_LAPD netccitt/x25.h:60
• HDLCPROTO_UNSET netccitt/x25.h:59