Doing this in current as of last night got me to make build cleanly.
(the one in /tmp with the const char is the one which works. the patch
 is probably diff'ed reversely.)

	-George


*** /usr/src/sys/lib/libkern/intoa.c	Sun Dec  5 09:58:49 1999
--- /tmp/intoa.c	Sun Dec  5 09:58:57 1999
***************
*** 44,54 ****
  #if defined(_KERNEL) || defined(_STANDALONE)
  #include <lib/libkern/libkern.h>
  #else
! char *intoa __P((u_int32_t)); /* XXX */
  #endif
  
  /* Similar to inet_ntoa() */
! char *
  intoa(addr)
  	u_int32_t addr;
  {
--- 44,54 ----
  #if defined(_KERNEL) || defined(_STANDALONE)
  #include <lib/libkern/libkern.h>
  #else
! const char *intoa __P((u_int32_t)); /* XXX */
  #endif
  
  /* Similar to inet_ntoa() */
! const char *
  intoa(addr)
  	u_int32_t addr;
  {
*** /usr/src/sys/lib/libkern/libkern.h	Sun Dec  5 09:58:28 1999
--- /tmp/libkern.h	Sun Dec  5 09:58:33 1999
***************
*** 156,162 ****
  int	 ffs __P((int));
  u_int32_t
  	 inet_addr __P((const char *));
! char	*intoa __P((u_int32_t));
  #define inet_ntoa(a) intoa((a).s_addr)
  void	*memchr __P((const void *, int, size_t));
  int	 memcmp __P((const void *, const void *, size_t));
--- 156,162 ----
  int	 ffs __P((int));
  u_int32_t
  	 inet_addr __P((const char *));
! const char	*intoa __P((u_int32_t));
  #define inet_ntoa(a) intoa((a).s_addr)
  void	*memchr __P((const void *, int, size_t));
  int	 memcmp __P((const void *, const void *, size_t));