DateFormatter: make TextToDate() long date calendar aware, tdf#125035
Using number formatter to display long date now can generate any
arbitrary date string in any calendar known to the locale. Cope
with non-default non-Gregorian calendars when parsing such string
back to a date and convert to Gregorian for the calendar widget.
This currently relies on month names being different between
calendars, which isn't fail-proof but at least works for the ar_DZ
Hijri->Gregorian case.
A better approach would be to remember the calendar used in the
number formatter output, but that's not available (yet?).
Change-Id: I829655275de4d1983b7e453624efca967b16a3bd
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/118449
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Jenkins