By substituting a (valid matching the type) format using these
special LCID modifier values with the current system locale's
format.

See ECMA-376-1:2016 18.8.31 numFmts (Number Formats) and
https://msdn.microsoft.com/en-us/library/documentformat.openxml.spreadsheet.numberingformats.aspx
which seems to be the only documentation available.

Change-Id: Ieca048a77d4ef473ae475e202557d1353ff5387d
Reviewed-on: https://gerrit.libreoffice.org/43148Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Jenkins <ci@libreoffice.org>