const-ify make segment ops structures
There is no reason to keep the segment ops structures writable.

*** 471,481 ****
                   * the insertion point is immediately before seg.
                   */
                  if (base + seg->s_size > addr) {
                          if (addr >= base || eaddr > base) {
  #ifdef __sparc
!                                 extern struct seg_ops segnf_ops;
  
                                  /*
                                   * no-fault segs must disappear if overlaid.
                                   * XXX need new segment type so
                                   * we don't have to check s_ops
--- 471,481 ----
                   * the insertion point is immediately before seg.
                   */
                  if (base + seg->s_size > addr) {
                          if (addr >= base || eaddr > base) {
  #ifdef __sparc
!                                 extern const struct seg_ops segnf_ops;
  
                                  /*
                                   * no-fault segs must disappear if overlaid.
                                   * XXX need new segment type so
                                   * we don't have to check s_ops
*** 2003,2013 ****
   * We're lazy and only return one segment at a time.
   */
  int
  as_memory(struct as *as, caddr_t *basep, size_t *lenp)
  {
!         extern struct seg_ops segspt_shmops;    /* needs a header file */
          struct seg *seg;
          caddr_t addr, eaddr;
          caddr_t segend;
  
          AS_LOCK_ENTER(as, &as->a_lock, RW_READER);
--- 2003,2013 ----
   * We're lazy and only return one segment at a time.
   */
  int
  as_memory(struct as *as, caddr_t *basep, size_t *lenp)
  {
!         extern const struct seg_ops segspt_shmops;      /* needs a header file */
          struct seg *seg;
          caddr_t addr, eaddr;
          caddr_t segend;
  
          AS_LOCK_ENTER(as, &as->a_lock, RW_READER);
*** 2480,2490 ****
          page_t **pl;
          int error;
          caddr_t eaddr;
          faultcode_t fault_err = 0;
          pgcnt_t pl_off;
!         extern struct seg_ops segspt_shmops;
  
          ASSERT(AS_LOCK_HELD(as, &as->a_lock));
          ASSERT(seg != NULL);
          ASSERT(addr >= seg->s_base && addr < seg->s_base + seg->s_size);
          ASSERT(addr + size > seg->s_base + seg->s_size);
--- 2480,2490 ----
          page_t **pl;
          int error;
          caddr_t eaddr;
          faultcode_t fault_err = 0;
          pgcnt_t pl_off;
!         extern const struct seg_ops segspt_shmops;
  
          ASSERT(AS_LOCK_HELD(as, &as->a_lock));
          ASSERT(seg != NULL);
          ASSERT(addr >= seg->s_base && addr < seg->s_base + seg->s_size);
          ASSERT(addr + size > seg->s_base + seg->s_size);