Found with modernize-avoid-bind
Signed-off-by: Rosen Penev <rosenp@gmail.com>

One basic library without dependencies, and one with heavy
dependencies like libsamplerate.

This reverts commit c84bae73.  A
configuration option is not necessary, because the PcmConvert
constructor knows already whether integer or floating point is needed.

This code path is 2% faster.

10% speedup.  Strange, huh?

For some reason, this speeds up the library by 2%.