These have changed a few times, notably in LO 4.0 with commit
89589056 and AOO 4.0 with commit
c0eb5e77; unfortunately historic OOo and
current AOO do not write the values into ODF files, whereas LO 4.x does
(probably by accident, since 45d3577b
by design).

Try to set the defaults depending on the generator; since the defaults
are not specified by ODF they are implementation defined anyway so this
should be OK.

Change-Id: I1270d6e0cdeea5cb493724a0998f661a0cf644f1