Ticket #54 - locale "nl" not supported by collation plugin
    
    Bug description: In the recent version of ICU, some locales do not
    have its specific collator, but are included in the default (root)
    locale.  "nl", "en", and "fr" are in the class.  ICU API ucol_open
    takes the locale string and returns the collator with the status.
    If the locale has no dedicated collator and the root collator is
    picked up, status U_USING_DEFAULT_WARNING is returned, which is not
    an error.  But collation_indexer_create (collate.c) treats it as an
    error and stops the collation.
    
    Fix description: As ICU doc suggests, error checking for ucol_open
    is replaced with "(U_SUCCESS(err)", by which the status U_USING_
    DEFAULT_WARNING is correctlly handled.
    
    https://fedorahosted.org/389/ticket/54
    
    Reviewed by rmeggins (Thank you, Rich!!)
    (cherry picked from commit c8d1cf570882a55329c11d8fba418c575671d131)