Additional annotation fixes

* At least one line (possibly blank) is required after a function name for a doc header
  to be parsed correctly.

* SnStartupSequence isn't a type known to introspection

src/core/screen.c

@@ -3241,10 +3241,10 @@ meta_screen_sn_event (SnMonitorEvent *event,
 }
 
 /**
- * meta_screen_get_startup_sequences:
+ * meta_screen_get_startup_sequences: (skip)
  * @screen:
  *
- * Return value: (transfer none) (element-type SnStartupSequence): Currently active #SnStartupSequence items
+ * Return value: (transfer none): Currently active #SnStartupSequence items
  */
 GSList *
 meta_screen_get_startup_sequences (MetaScreen *screen)

src/core/util.c

@@ -256,6 +256,7 @@ utf8_fputs (const char *str,
 
 /**
  * meta_free_gslist_and_elements: (skip)
+ *
  */
 void
 meta_free_gslist_and_elements (GSList *list_to_deep_free)
@@ -608,6 +609,7 @@ append_argument (GPtrArray  *args,
 
 /**
  * meta_show_dialog: (skip)
+ *
  */
 GPid
 meta_show_dialog (const char *type,