Switch export macros to standard form

Qt expects the export macros to have Q_ prefixes, otherwise the symbol
versioning script won't find them and mark them.

Task-number: QTBUG-74752
Change-Id: I1e057802f6715d170bdd9074f281e73fb96c9e52
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Kai Koehne <kai.koehne@qt.io>