wxMediaCtrl2 was never instantiated on any platform (USE_WX_MEDIA_CTRL_2
is 0 everywhere); wxMediaCtrl3 replaced it. Delete wxMediaCtrl2.cpp/h,
drop them from the Win/Linux source list and the gettext list.txt, and
collapse the preprocessor-dead #if USE_WX_MEDIA_CTRL_2 gate in
MediaPlayCtrl.h.
Co-Authored-By: Claude <noreply@anthropic.com>