plugin api: add the following functions.

- get the viewport of the current skin.
- update the current skin statusbar.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@27333 a1c6a512-1295-4272-9138-f99709370657

apps/plugin.c

@@ -565,6 +565,11 @@ static const struct plugin_api rockbox_api = {
     /* statusbars */
     &statusbars,
     gui_syncstatusbar_draw,
+#ifdef HAVE_LCD_BITMAP
+    sb_skin_get_info_vp,
+    sb_skin_update,
+#endif
+
     /* options */
     get_settings_list,
     find_setting,