After a seek failure, the buffer may still be full, and then
FillBuffer() aborts with assertion failure.

See https://picard.musicbrainz.org/docs/mappings/

This tag is useful when the user would like all releases of the same
album to be sorted next to each other.

upgrade zlib to 1.2.11

An ino_t is usually a 64 bit integer, and some file systems (such as
Linux's kernel NFS client) really uses the upper 32 bit.  This can
lead to false positives in the directory loop detection in
FindAncestorLoop().  Increasing these two attributes (in
StorageFileInfo and Directory) to 64 bit adds little overhead, but
makes the check a lot safer.

See code comment.  Bug was reported against MPD, but it's really an
alsa-lib bug.

 https://bugs.musicpd.org/view.php?id=4662

release v0.20.6

The TAG_MODIFIED handler (i.e. playlist::TagModified()) works only if
the modified song is the current song - something that is not updated
until SYNC_WITH_PLAYER is finished.  This fixes tag updates right
after a new song is started.

https://bugs.musicpd.org/view.php?id=4665

Just in case.

GCC7 outputs the following error without this change:

    src/util/ReusableArray.hxx:61:35: error: no matching function for call to ‘swap(size_t&, const size_t&)’
       std::swap(capacity, src.capacity);

which can be resolved by just using an rvalue-reference rather than a
const rvalue-reference.
Signed-off-by: Ben Boeckel <mathstuf@gmail.com>

Android is migrating away from GCC, and libstdc++ will disappear
eventually.

This repairs the damage to commit 74dbaade done by commit
b3f5b493

Fixes a GCC warning because %llu appears to be unsupported by the
Windows standard library.

https://bugs.musicpd.org/view.php?id=4656 describes a crash due to
division by zero because frame.samples==0.  This should never happen,
but apparently can happen after seeking.  The best we can do is to
just ignore this frame.