Attempt fixing mroonga gcc 8 build failure

Part of MDEV-19061 - table_share used for reading statistical tables is
                     not protected

storage/mroonga/mrn_table.cpp

@@ -932,7 +932,7 @@ MRN_SHARE *mrn_get_share(const char *table_name, TABLE *table, int *error)
         share->wrap_key_info = NULL;
         share->wrap_primary_key = MAX_KEY;
       }
-      memcpy(wrap_table_share, table->s, sizeof(*wrap_table_share));
+      *wrap_table_share= *table->s;
       mrn_init_sql_alloc(current_thd, &(wrap_table_share->mem_root));
       wrap_table_share->keys = share->wrap_keys;
       wrap_table_share->key_info = share->wrap_key_info;