Saving relative references of named expressions to OOXML never worked,
upon reload they pointed to a different position offset by the value of
the original base position. This at least saves positive relative
references correctly, while generating #REF! for negative offsets which
is slightly better than having them point to a wrong location and
silently calculate different values..

Also, this is a prerequisite for TableRef ThisRow references in named
expressions to be saved correctly in A1 notation, which results in a
relative row 0 value.

Change-Id: I3734f910794ceab4b9224b214ad11c64d1d18e67
(cherry picked from commit 80aafaf7)