Also remove unchecked memory allocation.

-O3 enables dangerous optimizations and does not make much sense for a
protocol (not decoding => not performance critical) library.

Close #7133

Close #6578

The code is far from being great, but it matches the Qt intf now.

Fix #1859 #6983

Depending on the system, this can be called ducking, focus, policy...
But it basically boils down to pausing playback automatically when a
higher priority audio stream starts, typically a voice call.

Resuming playback automatically when communications are over would be
possible as well. But that seems unfriendly to me, so I skipped it.

This was not tested due to lack of hardware.

This reverts commit 12627b88.

Modified-by: Rafaël Carré <funman@videolan.org>
Signed-off-by: Rafaël Carré <funman@videolan.org>

VLC has a native parser with higher priority. So ModPlug only got to
parse the broken files that VLC rejected. ModPlug is not robust and it
crashes in that case.

(support for webm and Opus)