[mythtv] Problems with dynamic_cast

[Peter Bennett]

In Android build with latest ndk -

In standardsettings.cpp
auto dce = dynamic_cast<DialogCompletionEvent*>(event)
the dynamic cast returns null even when the correct type is passed. I 
have changed that code to use a static cast in the Android case.

To see whether all dynamic_casts are failing I set a breakpoint at 
another dynamic_cast while running in Android and it is working correctly

tv_play.cpp:3952
auto *qke = dynamic_cast<QKeyEvent*>(e);
After that line is run the value of qke is not null, it is the same as 
the value of e.

This one is executed whenever you press a remote button while playing a 
recording.

So it is not a general failure, there must be some specific condition 
that affects standardsettings.cpp, or some corruption of data.

Peter