Use libvorbis instead of libvorbisfile, which gives us more control
over the decoding process.

This reverts commit 995cd954.  It was
a bad idea because it caused assertion failures when a decoder plugin
aborted with an exception.

Prepare to reuse the same code for a new Vorbis decoder plugin based
on libvorbis instead of libvorbisfile.

Allow decoders to throw std::runtime_error.

Initialize the OggStreamState as soon as the first page is seen; no
special code needed in the caller.

> In file included from src/decoder/DecoderBuffer.cxx:21:0:
> src/decoder/DecoderBuffer.hxx:41:20: error: 'uint8_t' was not declared in this scope
>   DynamicFifoBuffer<uint8_t> buffer;
>                     ^
> src/decoder/DecoderBuffer.hxx:41:27: error: template argument 1 is invalid
>   DynamicFifoBuffer<uint8_t> buffer;
>                            ^
> src/decoder/DecoderBuffer.hxx: In member function 'void DecoderBuffer::Clear()':
> src/decoder/DecoderBuffer.hxx:61:10: error: request for member 'Clear' in '((DecoderBuffer*)this)->DecoderBuffer::buffer', which is of non-class type 'int'
>    buffer.Clear();
>           ^
> src/decoder/DecoderBuffer.hxx: In member function 'size_t DecoderBuffer::GetAvailable() const':
> src/decoder/DecoderBuffer.hxx:78:17: error: request for member 'GetAvailable' in '((const DecoderBuffer*)this)->DecoderBuffer::buffer', which is of non-class type 'const int'
>    return buffer.GetAvailable();
>                  ^
> src/decoder/DecoderBuffer.hxx: In member function 'ConstBuffer<void> DecoderBuffer::Read() const':
> src/decoder/DecoderBuffer.hxx:87:19: error: request for member 'Read' in '((const DecoderBuffer*)this)->DecoderBuffer::buffer', which is of non-class type 'const int'
>    auto r = buffer.Read();
>                    ^
> src/decoder/DecoderBuffer.hxx:88:27: error: could not convert '{<expression error>, <expression error>}' from '<brace-enclosed initializer list>' to 'ConstBuffer<void>'
>    return { r.data, r.size };
>                            ^
> src/decoder/DecoderBuffer.hxx: In member function 'void DecoderBuffer::Consume(size_t)':
> src/decoder/DecoderBuffer.hxx:105:10: error: request for member 'Consume' in '((DecoderBuffer*)this)->DecoderBuffer::buffer', which is of non-class type 'int'
>    buffer.Consume(nbytes);
>           ^

This seems to be caused by a lacking include, fixed by the below patch.

I'm unsure what made this appear now, though, compiler and toolchain
libraries seem to be the same upstream versions that built 0.19.14-1
just fine in late March.

Fixes an assertion failure in tag_ape_scan() which is because
decoder_input_stream_open() returns an "unready" InputStream.

Required for OpusTags packets which contain artwork.

See https://bugs.musicpd.org/view.php?id=4520