Test struct sizes on 32-bit too.

src/bookmarks.rs

@@ -74,6 +74,15 @@ mod tests {
     use minidom::Element;
     use compare_elements::NamespaceAwareCompare;
 
+    #[cfg(target_pointer_width = "32")]
+    #[test]
+    fn test_size() {
+        assert_size!(Conference, 76);
+        assert_size!(Url, 24);
+        assert_size!(Storage, 24);
+    }
+
+    #[cfg(target_pointer_width = "64")]
     #[test]
     fn test_size() {
         assert_size!(Conference, 152);