Following resolution of tdf#117575, this commit add
disambiguation between '0' and '?' in integer part
XML_MAX_BLANK_INTEGER_DIGITS is added for the number of '?'
XML_MIN_INTEGER_DIGITS is the number of '?' and '0'
This preserve compatibility with previous versions:
in previous versions '?' will be transformed in '0'
It also applies to scientific and fraction numbers.

Change-Id: I6e1185bbece9c615240425cc973d59052b22aa34
Reviewed-on: https://gerrit.libreoffice.org/56352
Tested-by: Jenkins
Reviewed-by: Eike Rathke <erack@redhat.com>