Fixes hanging child process in the "pipe" output plugin.

Link libvorbisfile first, followed to libvorbis and finally libogg.
This order is necessary because libvorbisfile depends on libvorbis.

Fixes another linker failure.  Similar to commit ea406875

Since the encoder plugin uses a libvorbis function (and not only
libvorbisenc functions), we need to link with libvorbis explicitly.

Allow semicolons and single quotes in the stream title.  This is not
part of any specification, but found in real life.

Works around a build failure on Solaris because annoyingly, Solaris
reserves the name "queue".  This rename was pending anyway.

Fixes potential nullptr dereference.

Fixes clang warning.

Look for symbol "mpc_demux_init" which does not exist in SV7.  This
avoids build failures when SV7 was found by configure.ac.

A file called ".jpg" is not a JPEG file with an empty name; it is
merely a hidden file.

If we have libyajl 2.0.1 (without a pkg-config file), our configure.ac
would assume this is the libyajl 1.0 API, because the function
yajl_alloc() exists in both.  This commit changes the library check to
the function yajl_parse_complete() which was removed in the 2.0 API.
This fixes build failure with libyajl 2.0.1.

We can assume that initgroups() would be a no-op in that case, however
initgroups() is not allowed for unprivileged users anyway.

The "mode" of the second ReplayGainFilter was never set, and thus
replay gain was never applied to the new song during cross-fade.

For std::move().

Some tagging libraries (eg. TagLib) produce that variant.

Broken by commit 3b0fea5f

This deadlock was a regression by commit 8e38b4f8.  Since we currently
can't resolve this, let's revert the commit, and add a GLib specific
workaround for the build failure.