old code used to use XCell->setString, new code uses rDoc.SetString which by default tries to detect number formats. The ScColumn::SetString that eventually
gets called seems to do lots of additional checks ( and apparently even if
an ScSetStringParam instance with mbDetectNumberFormat ( false ) was passed
it seems that it will still try to detect decimal number formats. With that
in mind I restore and un-unoified version of what XCell->setString used do

Change-Id: Ifaef74c78b198f492a390a3d5dc1721622a01ea4