to support variants of preposition, suffixation,
article or their combination. For example, Catalan
"de març"/"d'abril", English "1st of May"/"First of
May" or Hungarian "május 1-je/május 2-a".

When the date format contains more than a date keyword,
it needs to specify in NatNum12 argument which date
element needs special formatting by using libnumbertext:

'[NatNum12 ordinal-number]D'              -> "1st"
'[NatNum12 D=ordinal-number]D" of "MMMM'  -> "1st of April"
'[NatNum12 D=ordinal]D" of "MMMM'         -> "first of April"
'[NatNum12 YYYY=year,D=ordinal]D" of "MMMM", "YYYY' ->
"first of April, nineteen ninety"

Note: set only for YYYY, MMMM, M, DDDD, D and NNN/AAAA
in date formats. It's possible to extend this for other
keywords and date + time combinations, as required.

Note 2: default l10n date formats can use the new NatNum12 date
formats, see FormatElement in i18npool/source/localedata/
XML files and FormatElement specification:
https://opengrok.libreoffice.org/xref/core/i18npool/source/localedata/data/locale.dtd#223

Change-Id: I598849f1492f4012e83cef9293773badbff16206
Reviewed-on: https://gerrit.libreoffice.org/55613Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: László Németh <nemeth@numbertext.org>