See code comment.

First check if an IPv6 socket can be created.

Map LogLevel::INFO to G_LOG_LEVEL_INFO, and LogLevel::DEFAULT to
G_LOG_LEVEL_MESSAGE.  Now client connect/disconnect message are only
logged on log_level "secure".

Fixes bogus test failures on Debian build machines due to rounding
errors (hopefully).

Regression from previous commit.  D'oh!

Use a std::list which can be appended at the end.

getnameinfo() doesn't work well - it always returns "localhost".

This prevented using the "volume_normalization" feature with some
codecs (e.g. mp3), because the normalization code requires 16 bit
samples.  If the codec happens to deliver formats other than S16, the
AutoConvert filter succeeds to initialize the conversion filter, but
the returned input audio format was wrong.

Skip the global destructors.  We don't need them here - we bail out as
quickly as we can.

Fixes assertion failure.

mixramp_delay==nan() causes severe problems with cross-fading.

2 MB was too small for cross-fading a 24 bit file.  Increasing to 4 MB
is still not too large for weak machines, but is enough for
cross-fading.

Without -Werror, clang will not fail on -ftree-vectorize.

Allows advanced compiler optimization.

Most importantly: always disable C++ exceptions.  It was surprising to
see MPD terminate due to an unexpected exception.

The last piece to allow -ffast-math.

Avoid NaN to allow -ffast-math.

Use a boolean flag instead.

Avoid NaN to allow -ffast-math.

Avoid NaN to allow -ffast-math.

Fixes crash.