always expand ivar arrays to max width

If the instance variable table hasn't been "expanded", allocate the
maximum size of the ivar table.  This operates under the assumption that
most objects will eventually expand their ivar array to the maximum
width anyway, so we may as well avoid realloc calls.

variable.c

@@ -896,8 +896,7 @@ iv_index_tbl_newsize(struct ivar_update *ivup)
     uint32_t index = (uint32_t)ivup->index;	/* should not overflow */
     uint32_t newsize = (index+1) + (index+1)/4; /* (index+1)*1.25 */
 
-    if (!ivup->iv_extended &&
-        ivup->u.iv_index_tbl->num_entries < (st_index_t)newsize) {
+    if (!ivup->iv_extended) {
         newsize = (uint32_t)ivup->u.iv_index_tbl->num_entries;
     }
     return newsize;