Fix incorrect calls to *scanf_s functions.

The documentation is quite unclear but it seems that all buffer sizes should be given as characters count rather bytes count.

Note that although the calls were incorrect, there was probably no real effect for users.
DVB: Fix default audio track selection when its type is different than
first audio track.

This commit fixes ticket #2396
DVB: Remember audio and subtitle track selection.

Remove audio selection menu from navigation dialog. We don't need it
anymore.
PPageCapture: Disable when no device is found.

Select Microsoft Network Provider by default, other network providers are
deprecated.
DVB: Set channel after scan dialog close
Remove D2VSource.  It's unmaintained and basically unused.