When I load an ODG document page, which is 5080 mm wide, then the UI
told me that it's 300 cm wide, which was misleading.

There is no real reason why the limit can't be higher, the draw page
size is sal_Int32 and the unit is either twips or mm100s: in both cases
sal_Int32 is more than enough to store the new limit still.

Change-Id: Ifb501eed4e288281bcc73dce71bdb03ac213b0c1
Reviewed-on: https://gerrit.libreoffice.org/69673Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins