The following 3 attributes have been added in ODF 1.2, so don't write
them into ODF 1.1 files:

style:layout-grid-base-width 20.297
style:layout-grid-snap-to 20.305
style:layout-grid-standard-mode 20.306

Additionally, style:layout-grid-snap-to was written wrongly as
style:layout-grid-snap-to-characters, which does not exist in any ODF
spec.
For backward compatibility with previous OOo/LO versions, write the
wrong attribute in addition to the correct one in ODF extended mode,
even though validators complain about it (consider removing that
some years from now).