I send earlier a diff, but it was incomplete.
I was in the middle of updating my two weeks old sources and forgot db_interface.c.
Here is it:

*** db_interface.c-orig	Sun Mar 17 13:24:11 1996
--- db_interface.c	Fri Mar 29 23:03:31 1996
***************
*** 33,51 ****
--- 33,60 ----
  #include <sys/proc.h>
  #include <sys/reboot.h>
  #include <sys/systm.h> /* just for boothowto --eichin */
+ #include <dev/cons.h>
  
  #include <vm/vm.h>
  
  #include <machine/trap.h>
  #include <machine/db_machdep.h>
  
+ #include <ddb/db_command.h>
+ #include <ddb/db_sym.h>
+ #include <ddb/db_extern.h>
+ 
  extern label_t	*db_recover;
+ void	kdb_kintr __P((struct mc68020_saved_state *));
+ int	kdb_trap __P((int, struct mc68020_saved_state *));
+ void	kdbprinttrap __P((int, int));
  
  int	db_active = 0;
  
  /*
   * Received keyboard interrupt sequence.
   */
+ void
  kdb_kintr(regs)
  	register struct mc68020_saved_state *regs;
  {
***************
*** 59,64 ****
--- 68,74 ----
   * kdb_trap - field a TRACE or BPT trap
   * Return non-zero if we "handled" the trap.
   */
+ int
  kdb_trap(type, regs)
  	int	type;
  	register struct mc68020_saved_state *regs;
***************
*** 123,128 ****
--- 133,139 ----
  /*
   * Print trap reason.
   */
+ void
  kdbprinttrap(type, code)
  	int	type, code;
  {