* lang/cpp/context.cpp, lang/cpp/context.h
(Context::startPublicKeyExport, Context::exportPublicKeys): Extend
with flags paramenter.
(Context::ExportMode): New.
* lang/qt/src/exportjob.h (ExportJob::setExportMode): New.
* lang/qt/src/qgpgmeexportjob.cpp, lang/qt/src/qgpgmeexportjob.h:
Update accordingly.