make_pair is an old C++98 function that can be replaced by modern
shorter constructs.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Insert an "aformat" filter which converts double-precision to
single-precision.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1235

Merge some duplicate code.

Since AVFilterContext are freed automatically, this wrapper class
serves no purpose.  Let's remove it.

Fixes potential double-free bugs which currently did not occur because
the destructors happened to be called in the right order.

bad_alloc depends on <new>