Sync with the Android NDK build scripts.

This flag is used by the Android NDK build scripts as well, and this
fixes a build failure (assembler error) with FFmpeg and NDK r21.

Fixes regression from commit db93bb99 because
ParseMimeTypeParameters() assumed the items were null-terminated, but
after that commit, they were not anymore.

The `db->close()` call was a `nullptr` dereference because the `db`
variable had already been moved.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/839

This is the final piece of the series to establish io_uring support on
Linux.

MPD doesn't need io_uring for its efficient bulk I/O support, but to
allow file I/O to be cancelled.  This is a big problem on CIFS/NFS
mounts where processes sleep uninterruptable if the file server
disappears, deadlocking MPD.

With io_uring, a flaky NFS connection allows MPD to continue to work
(even though there are still deadlocks inside MPD which need to be
addressed).

This plugin does not yet use cancellable `open()` using
`IORING_OP_OPENAT`.  This will be implemented later.

Lots of other optimization opportunities for io_uring are still
missing as well - for example the database update could benefit a lot,
but unfortunately, io_uring doesn't have `readdir()` support just yet.

Relax the assertions.  This is necessary if BlockingCall() is used
before the thread is started.

This makes ccache more efficient when recompiling with different
plugins.

Reduces unstripped size. stripped size is the same.

Also took the time to remove using std::placeholders.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

The command is used to configure the client's connection, and this
shouldn't require any permissions.  The client should be able to do
that before sending a password.

This reverts commit a5273d69.  It was
wrong and broke the MixRamp unit test.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/844

_GLIBCXX_USE_C99_MATH_TR1 is the correct one.

_GLIBCXX_USE_C99_MATH is always defined.

The parser implemented in libmpdclient requires the first key-value pair
of the server response to be the file pair. This is due to the fact that
libmpdclient scan pairs sequentially and first attempts to extract the
file pair before parsing the currentsong response further. See:

	https://github.com/MusicPlayerDaemon/libmpdclient/blob/5c751a761ec9f71a43ee0e41cfff3208f31a58b8/src/song.c#L559-L563

Meta data encoded as pairs in the currentsong response will be ignored
if they are placed before the file pair in the response.

Fixes breakage of non-ASCII characters, regression from commit
cc72ceb3

Fixes https://github.com/MusicPlayerDaemon/MPD/issues/842

Prepare to fix cc72ceb3

Also include fade-out time in song length.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/838

This reduces resource waste for resizing the std::vector in most
cases.

Optimizes a few nanoseconds from the common code path.