Some abstraction for decoder_control.pipe access.

Duplicate the "mime" attribute of the inner input_stream object,
instead of copying the pointer.

Same as ".m4a".

Change the assertion on "fail_timer==NULL" in OPEN to a runtime check.
This assertion crashed when the output thread failed while the player
thread was calling audio_output_open().

Protect the attributes "open" and "fail_timer".

Protect the attributes "open" and "fail_timer".

RFC 5334 10.3 defines the MIME type "audio/ogg".  We could use
"application/ogg" as well, but we know for sure that we only emit
audio data.

The assumption that MIME type is set only once is not valid with CURL,
as URL redirections may update the MIME type.

This fixes bug #3044.

This caused random data to be send via icy-server if the played
song had no tags.

According to the CURL web site, curl_multi_timeout() was added in
version 7.15.4:

 http://curl.haxx.se/libcurl/c/curl_multi_timeout.html

Clear the notification before finishing the CANCEL command, so the
notify_wait() after that will always wait for the right notification,
sent by audio_output_all_cancel().

Some users reported that MPD crashes when using a new CURL version
with the threaded DNS resolver enabled.  It seems that
curl_multi_fdset() returns no file descriptor when the DNS resolver
runs in another thread, so MPD does not have any event to wait for.

On the CURL mailing list, somebody suggested to sleep for a fixed
amount of time.  This is not an elegant solution, because daemons
should never have to sleep without waiting for an event.  I hope the
CURL developers will review the API and remove the threaded DNS
resolver.

Meanwhile, I'm removing the assertion in question, to allow those
unfortunate users running the latest CURL version to continue using
MPD.

Use curl_multi_timeout() to determine the select() timeout, instead of
hard-coding one second.

RVA2 tags only store the "gain" value, there is no "peak" attribute.

In libwildmidi 0.2.3, the function WildMidi_SampledSeek() was removed,
without changing the SO name.  This patch adds an autoconf check for
that function.  Fall back to WildMidi_FastSeek() if
WildMidi_SampledSeek() is not available anymore.

libavformat 0.6 does not pass the original URI pointer to the "open"
method, which leads to a crash because MPD was using a dirty hack to
pass a pointer to that method.

This patch switches to av_open_input_stream() with a custom
ByteIOContext class, instead of doing the URI string hack with
av_open_input_file().

Loosely based on a patch from Jasper St. Pierre.

Use the libavformat function av_probe_input_format() to probe the
AVInputFormat, instead of letting av_open_input_file() do it
implicitly.  We will switch to av_open_input_stream() very soon, which
does not have the probing code.

Loosely based on a patch from Jasper St. Pierre.

Free the string allocated by decoder_get_uri().

This fixes a theoretical crash, which has never occurred in practice.

Fix a memory leak in some code paths.

Replace the check for avcodec_decode_audio2(), assume it's present in
libavcodec version 51.

We already supported "albumartist", but it seems some folks also use
"album artist" (with a space).

I've attached a patch that will make file URIs work on operating systems
that provide the getpeereid() function call to check the user ID of the
peer connected to a UNIX domain socket.

There is no useful return value here.