dccp: snoop, build system fixes

*** 236,245 ****
--- 236,247 ----
  extern int interpret_udp(int, struct udphdr *, int, int);
  extern int interpret_esp(int, uint8_t *, int, int);
  extern int interpret_ah(int, uint8_t *, int, int);
  struct sctp_hdr;
  extern void interpret_sctp(int, struct sctp_hdr *, int, int);
+ struct dccphdr;
+ extern int interpret_dccp(int, struct dccphdr *, int, int);
  extern void interpret_mip_cntrlmsg(int, uchar_t *, int);
  struct dhcp;
  extern int interpret_dhcp(int, struct dhcp *, int);
  extern int interpret_dhcpv6(int, const uint8_t *, int);
  struct tftphdr;