Use new g_memdup2 if available.

This mostly addresses a deprecation warning. We can get rid of the
ifdefs if we decide to simply bump the required version.

src/gst/audio/plugin.c

@@ -57,7 +57,11 @@ bt_g_param_spec_clone (GObjectClass * src_class, const gchar * src_name)
 
   g_type_query (G_PARAM_SPEC_TYPE (src), &query);
   /* this is pretty lame, we have no idea if we copy e.g. pointer fields */
+#if GLIB_CHECK_VERSION(2, 68, 0)
+  pspec = g_memdup2 (src, (gsize) query.instance_size);
+#else
   pspec = g_memdup (src, query.instance_size);
+#endif
   /* reset known fields, see g_param_spec_init() */
   pspec->owner_type = 0;
   pspec->qdata = NULL;

src/lib/core/song-io-native-bzt.c

@@ -396,7 +396,11 @@ bt_song_io_native_bzt_save (gconstpointer const _self,
             gsf_off_t len = gsf_output_size (self->priv->output);
             const guint8 *mem = gsf_output_memory_get_bytes (
                 (GsfOutputMemory *) self->priv->output);
+#if GLIB_CHECK_VERSION(2, 68, 0)
+            gpointer data = g_memdup2 (mem, (gsize) len);
+#else
             gpointer data = g_memdup (mem, (guint) len);
+#endif
             g_object_set ((gpointer) self, "data", data, "data-len",
                 (guint) len, NULL);
           }

src/lib/core/song-io-native-xml.c

@@ -122,7 +122,11 @@ bt_song_io_native_xml_save (gconstpointer const _self,
         gpointer data;
 
         xmlDocDumpMemory (song_doc, &mem, (int *) &len);
+#if GLIB_CHECK_VERSION(2, 68, 0)
         data = g_memdup2 (mem, len);
+#else
+        data = g_memdup (mem, len);
+#endif
         xmlFree (mem);
         g_object_set ((gpointer) self, "data", data, "data-len", len, NULL);
       }

src/ui/edit/main-page-patterns.c

@@ -1819,12 +1819,22 @@ pattern_table_refresh (const BtMainPagePatterns * self)
             pid, j);
         group->num_columns = self->priv->voice_params;
         group->columns =
+#if GLIB_CHECK_VERSION(2, 68, 0)
+            g_memdup2 (stamp->columns,
+                sizeof (BtPatternEditorColumn) * group->num_columns);
+#else
             g_memdup (stamp->columns,
-            sizeof (BtPatternEditorColumn) * group->num_columns);
+                sizeof (BtPatternEditorColumn) * group->num_columns);
+#endif
         for (i = 0; i < group->num_columns; i++) {
           group->columns[i].user_data =
+#if GLIB_CHECK_VERSION(2, 68, 0)
+              g_memdup2 (group->columns[i].user_data,
+                  sizeof (BtPatternEditorColumnConverters));
+#else
               g_memdup (group->columns[i].user_data,
-              sizeof (BtPatternEditorColumnConverters));
+                  sizeof (BtPatternEditorColumnConverters));
+#endif
         }
         group->width = 0;
         group++;