MainWindow: use header for ArchiveRestoreOptions
MainWindow: use header for ArchiveRestoreOptions

This isn't necessary right now, because we're getting the definition of
ArchiveRestoreOptions from "jobstabwidget.h".  However, once we finish
pointerifying "mainwindow.h", we would be left without a necessary
definition.

Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui