2976 remove useless offsetof() macros

*** 24,43 ****
   */
  
  #ifndef _MDBMOD_MISC_H
  #define _MDBMOD_MISC_H
  
- #pragma ident   "%Z%%M% %I%     %E% SMI"
- 
  #include <mdb/mdb_modapi.h>
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
- #define offsetof(s, m)  ((size_t)(&(((s *)0)->m)))
- 
  extern int umem_debug(uintptr_t, uint_t, int, const mdb_arg_t *);
  
  extern int umem_set_standalone(void);
  extern ssize_t umem_lookup_by_name(const char *, GElf_Sym *);
  extern ssize_t umem_readvar(void *, const char *);
--- 24,40 ----
   */
  
  #ifndef _MDBMOD_MISC_H
  #define _MDBMOD_MISC_H
  
  #include <mdb/mdb_modapi.h>
+ #include <stddef.h>
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  extern int umem_debug(uintptr_t, uint_t, int, const mdb_arg_t *);
  
  extern int umem_set_standalone(void);
  extern ssize_t umem_lookup_by_name(const char *, GElf_Sym *);
  extern ssize_t umem_readvar(void *, const char *);