Defines starting with `h' in netccitt

• HDHEADERLN netccitt/hdlc.h:92
• HDLC netccitt/ccitt_proto.c:40
• HDLCPROTO_LAP netccitt/x25.h:53
• HDLCPROTO_LAPB netccitt/x25.h:54
• HDLCPROTO_LAPD netccitt/x25.h:56
• HDLCPROTO_UNSET netccitt/x25.h:55