qt: Replace Q_DECL_OVERRIDE with override
* lang/qt/src/defaultkeygenerationjob.h, lang/qt/src/hierarchicalkeylistjob.h, lang/qt/src/multideletejob.h, lang/qt/src/protocol_p.h, lang/qt/src/qgpgmeadduseridjob.h, lang/qt/src/qgpgmechangeexpiryjob.h, lang/qt/src/qgpgmechangeownertrustjob.h, lang/qt/src/qgpgmechangepasswdjob.h, lang/qt/src/qgpgmedecryptjob.h, lang/qt/src/qgpgmedecryptverifyjob.h, lang/qt/src/qgpgmedeletejob.h, lang/qt/src/qgpgmedownloadjob.h, lang/qt/src/qgpgmeencryptjob.h, lang/qt/src/qgpgmeexportjob.h, lang/qt/src/qgpgmegpgcardjob.h, lang/qt/src/qgpgmeimportfromkeyserverjob.h, lang/qt/src/qgpgmeimportjob.h, lang/qt/src/qgpgmekeyformailboxjob.h, lang/qt/src/qgpgmekeygenerationjob.h, lang/qt/src/qgpgmekeylistjob.h, lang/qt/src/qgpgmelistallkeysjob.h, lang/qt/src/qgpgmenewcryptoconfig.h, lang/qt/src/qgpgmequickjob.h, lang/qt/src/qgpgmerefreshsmimekeysjob.h, lang/qt/src/qgpgmesignencryptjob.h, lang/qt/src/qgpgmesignjob.h, lang/qt/src/qgpgmesignkeyjob.h, lang/qt/src/qgpgmetofupolicyjob.h, lang/qt/src/qgpgmeverifydetachedjob.h, lang/qt/src/qgpgmeverifyopaquejob.h, lang/qt/src/qgpgmewkdlookupjob.h, lang/qt/src/qgpgmewkspublishjob.h, lang/qt/src/threadedjobmixin.h, lang/qt/tests/t-support.h: Replace Q_DECL_OVERRIDE with override
We require C++11 since a long time.