.. and move the plugins to src/encoder/plugins/.

Initializing and closing the Shine library without
writing any data results in a segmentation fault.
The current workaround writes zeroes if there was
no actual data.

Now writes to the de-interleaved buffers directly,
instead of writing to an intermediate fifo buffer.

Fix indentation and 80 char width lines.

This encoding plugin features a fixed-point mp3 encoder,
with faster encoding on architectures without a FPU.

Right now the encoder is limited to stereo and 16 bit depth.
The bitrate and sample rate can be modified in audio_output.

audio_output {
        type            "httpd"
        name            "My shine stream"
        encoder         "shine"
        port            "8000"
        format          "44100:16:2"
        bitrate         "320"  # default: 128
}

Replacing GLib macros.

Prepare to migrate away from GLib.  Currently, we're still using GLib
as a backend.

The MPD core will add this as a prefeix.

Replaces GLib's GError.

Don't deinterleave manually, don't allocate memory.

I recently opened a bug: http://bugs.musicpd.org/view.php?id=3787

The main problem is that opus encoder config for signal overwrote
bitrate setting.