make this file portable to compilers other than gcc 4

git-svn-id: file:///svn/tokudb@100 c7de825b-a66e-492c-adef-691d508d4ae1

newbrt/list.h

@@ -60,7 +60,11 @@ static inline void list_move(struct list *newhead, struct list *oldhead) {
     list_init(oldhead);
 }
 
+#if defined(__GNUC__) && __GNUC__ >= 4
 #define list_struct(p, t, f) (t*)((char*)(p) - __builtin_offsetof(t, f))
+#else
+#define list_struct(p, t, f) (t*)((char*)(p) - ((char*)&((t*)0)->f))
+#endif