QShortcut:: should be able to produce a list of all conflicting shortcuts

QShortcut:: should be able to produce a list of all shortcuts that are in conflict in the current context.

The QShortct::ActivaedAmbiguously signal should be emitted from all matching shortcuts and not just one, or a new function should be implemented that returns this list. This way the user would know which shortcuts are in conflict (with the currently pressed one) in the current context.