This is needed to build libFLAC which uses ftello().

The `dump` command was dropped[1] in favor of other tools.

[1]: https://gitlab.freedesktop.org/pipewire/pipewire/-/commit/50bdebe4e87c5e26acf966e7207a591332e33239

systemd uses "rootprefix", not "prefix" for this value

https://github.com/systemd/systemd/blob/059b1b31ade7f1d716f56c5e6fd657ce22ce2032/src/core/systemd.pc.in#L23

See https://www.bassi.io/articles/2018/03/15/pkg-config-and-paths/

Fixes the build in nixpkgs

6d91b5c7 ("fix double promotions") changed
how LAME peak values are decoded, producing large incorrect values that
cause some MP3 files to play silently.

Restore the original decode from MAD fixed-point format to double and
document what it's doing.

Fixes #1823

With sphinx-build 5.0.0:
doc/user.rst:728: ERROR: Unexpected indentation.
doc/user.rst:731: ERROR: Unexpected indentation.

Let OnHeaders() check the status.

The status checking code was added by commit 4f021cbc in 2011,
but in 2008, commit a8e81326 enabled `CURLOPT_FAILONERROR`, which
means the status checking code never had any effect.

This allows `LoadExcludeListOrLog()` to hide boring "404 Not Found"
log messages via `IsFileNotFound()`.

The `assert(!quit)` can fail if the `EventThread` gets stopped before
it enters `EventLoop::Run()`. There is a similar problem with `alive`,
which gets reset by `EventThread::Stop()`.

If that happens, then `EventLoop::Run()` should return immediately
without handling any events.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1785

Without clearing all `in_playlist` flags, the songs will never be
revealed again if they were hidden once by a CUE sheet, not even after
the CUE sheet gets deleted or modified.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1784

Fixes GCC 10 error:

 error: cannot call member function `Foo` without object

Fixes crash inside AtScopeExit() in the WASAPI output plugin.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1759

This adds `MakeFfmpegError()` to the executable and fixes a linker
failure when `libavutil` is available, but `libavformat` and
`libavcodec` are not.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1786

Otherwise, building will generate these warnings:

systemd/system/meson.build:5: WARNING: Project targeting '>= 0.56.0' but tried to use feature deprecated since '0.56.0': Dependency.get_pkgconfig_variable. use Dependency.get_variable(pkgconfig : ...) instead
systemd/user/meson.build:5: WARNING: Project targeting '>= 0.56.0' but tried to use feature deprecated since '0.56.0': Dependency.get_pkgconfig_variable. use Dependency.get_variable(pkgconfig : ...) instead