Cut and paste solution to get export working. The issue is that the old

Cut and paste solution to get export working. The issue is that the old
exportAndDestroy was calling:
  buffer->doExport(format, true, update_unincluded);
where "true" means: Leave it in the tempdir. We need false, which means
we need another parameter, if we're not doing it as cut and paste.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@35715 a592a061-630c-0410-9148-cb99ea01b6c8