[PVR] Timeshifting: Fixed EpgInfoTag::[IsActive|WasActive|InTheFuture]

Changed EpgInfoTag::[IsActive|WasActive|InTheFuture] to take timeshifting into account. 
Fixes wrong event info shown at several places in kodi UI when timeshifting (e.g. Video OSD).
C'mon! Sure it can... I could write the whole code even much more compact, but isn't coding somehow, up to a certain point personal style (as long as it does not conflict with project's coding guidelines)? Being a nitpicker myself, but this goes a little to far, imho.