dup_summary_for_locale
Description:
Returns a summary for the given locale.
 When locale is null, the current locale is assumed. If no such summary for the locale exists 
      either a summary with no language parameter or the first found is returned.
Free the returned non-NULL ComponentText with e_cal_component_text_free
      , when no longer needed.
Parameters:
| this | A calendar component object. | 
| locale | a locale identifier, or null | 
Returns:
| summary for the  |