IncomingFileTransferChannel: Make acceptFile require FileTransferChannel::FeatureCore.
IncomingFileTransferChannel: Make acceptFile require FileTransferChannel::FeatureCore.

This is needed cause the handling of acceptFile requires a proper
FileTransferStateChanged handling.

TelepathyQt/telepathy-qt,tiagosh/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt4,TelepathyQt/telepathy-qt,TelepathyIM/telepathy-qt,special/telepathy-qt-upstream,tiagosh/telepathy-qt,TelepathyQt/telepathy-qt,TelepathyIM/telepathy-qt,tiagosh/telepathy-qt,tiagosh/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt4,special/telepathy-qt-upstream,detrout/telepathy-qt,anantkamath/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt,TelepathyIM/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt4,TelepathyIM/telepathy-qt,detrout/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt,anantkamath/telepathy-qt,TelepathyQt/telepathy-qt,special/telepathy-qt-upstream,detrout/telepathy-qt,anantkamath/telepathy-qt,freedesktop-unofficial-mirror/telepathy__telepathy-qt4,freedesktop-unofficial-mirror/telepathy__telepathy-qt,TelepathyIM/telepathy-qt