server/gstdecode.c: Produce the configured sample format directly.

server/gstdecode.c: Produce the configured sample format directly.

Introduce a GStreamer resampler, which is benign (and fast) if it has
nothing to do, and set the sink caps to match the configured audio
format.  Hopefully, the normalizer is now trivial.

This means that we must fetch the configuration file, which involves
adding gcrypt to the link.