gobject: Use g_memdup2() instead of g_memdup() in obvious places

Convert all the call sites which use `g_memdup()`’s length argument
trivially (for example, by passing a `sizeof()`), so that they use
`g_memdup2()` instead.

In almost all of these cases the use of `g_memdup()` would not have
caused problems, but it will soon be deprecated, so best port away from
it.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Helps: #2319

gobject/tests/param.c

@@ -903,7 +903,7 @@ main (int argc, char *argv[])
             test_path = g_strdup_printf ("/param/implement/subprocess/%d-%d-%d-%d",
                                          data.change_this_flag, data.change_this_type,
                                          data.use_this_flag, data.use_this_type);
-            test_data = g_memdup (&data, sizeof (TestParamImplementData));
+            test_data = g_memdup2 (&data, sizeof (TestParamImplementData));
             g_test_add_data_func_full (test_path, test_data, test_param_implement_child, g_free);
             g_free (test_path);
           }