When a reference counter is at its limit, don't allocate a new
TagPoolSlot - that would result in many TagPoolSlot instances with
ref==1.  This in turn would make the linked list very very large,
which means quadratic runtime for many operations.

Avoid wasting 4 kB stack per directory level.

There were two ways this could fail:

1. division by zero when sysconf(_SC_PAGESIZE)==0

2. mmap() failure because the size parameter is not aligned to page
   size

Neither ever happened: sysconf() never fails, and the only caller
passes a size that is already aligned.  Phew.

The old check

 unsigned(value) > std::numeric_limits<unsigned>::max()

.. cannot ever fail.

Apparently all other C libraries are not compatible with "constexpr".
Those which are not will get a performance penalty, but at least they
work at all.

Fixes disappearing duration of remote songs during playback.

See http://bugs.musicpd.org/view.php?id=4492

The initgroups() manpage says we need to check for _BSD_SOURCE.  The
thing is that glibc deprecated this macro, and doesn't define it
anymore, effectively breaking all MPD supplementary groups.

The real fix is to check for initgroups() availability at configure
time, instead of relying on the deprecated _BSD_SOURCE macro.

Apply padding only to the fseek(), not to the chunk size.  This fixes
bogus "failed to read riff chunk" messages when the last chunk has an
odd size.

See http://bugs.musicpd.org/view.php?id=4486

These are other popular clients. In particular, VLC is available on
mobile devices.
Signed-off-by: Ben Boeckel <mathstuf@gmail.com>

systemd does not understand LimitRTTIME=-1. For no limit we have to use
the string 'infinity' (see systemd.exec(5)).
Signed-off-by: Christian Hesse <mail@eworm.de>

Add ALSA_LIBS to MIXER_LIBS, otherwise building mpd in a static context fails
with lot of undefined references to alsa-lib (libasound) required by
src/mixer/plugins/AlsaMixerPlugin.cxx.
Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>

This systemd feature has been removed a while ago without replacement,
and it turns out that systemd developers suggest not using control
groups at all to assign real-time privileges.  Therfore, a replacement
feature will not be implement in future systemd releases, and we can
really remove those lines completely.

See http://bugs.musicpd.org/view.php?id=4413

Fixes http://bugs.musicpd.org/view.php?id=4432

Fixes mixer lag (http://bugs.musicpd.org/view.php?id=4425).

Allocate the buffer dynamically using av_malloc(), and free
AVIOContext.buffer in the destructor, as mandated by the libavformat
documentation.

Fixes http://bugs.musicpd.org/view.php?id=4446

Eliminates some duplicate code, and as a side effect, this works
around clang 3.8 compiler warning because a negative value was
shifted.