Update notificator.cpp

Fix old error of compilation file "notificator.cpp":
"src/qt/notificator.cpp: In constructor ‘FreedesktopImage::FreedesktopImage(const QImage&)’:
src/qt/notificator.cpp:116: error: ‘class QImage’ has no member named ‘constBits’"
Merge pull request #2 from awoland/patch-1

Update notificator.cpp