2976 remove useless offsetof() macros

@@ -24,20 +24,17 @@
  */
 
 #ifndef _MDBMOD_MISC_H
 #define _MDBMOD_MISC_H
 
-#pragma ident   "%Z%%M% %I%     %E% SMI"
-
 #include <mdb/mdb_modapi.h>
+#include <stddef.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 *);