Fix Saorview MHEG problems

In MHEngine::GenerateUserAction? the current scene is passed to EventTriggered?
 , but Saorview MHEG works if the current app is passed instead. This change does not seem to break BBC MHEG.

 This is from MHEG-5 Broadcast Profile (ETSI ES 202 184), and I'm assuming there's something similar in the Corrigenda to the UK Profile (the Corrigenda doesn't seem to be available from dtg.org.uk any more).:
UniversalEngineProfile(N)

Receivers based on the present document but which have not been
verified as fully conformant shall not return true when N=1 285. Instead
they shall return true when N=2.

 Saorview expects UEP(1285) to return true, MythTV returns true for UEP(2), but not UEP(1285).

 Also there are bugs in MHText and MHLineArt.

Signed-off-by: Stuart Morgan <smorgan@mythtv.org>