The ones in std have overloads for const char/char.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

This is needed to correctly load playlist entries that reference a song in a cuesheet that is treated as a folder.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/607

Since we switched from autotools to Meson in commit
94592c14, we don't need to include
`config.h` early to properly enable large file support.  Meson passes
the required macros on the compiler command line instead of defining
them in `config.h`.

This means we can include `config.h` at any time, whenever we want to
check its macros, and there are no ordering constraints.

Fixes aborted "load" commands due to SongLoader failure.

Now that Song::GetDuration() is used (which considers start_ms and
end_ms), we don't need to override the Tag's duration value.

Playback with some decoder plugins was broken because the Queue's
DetachedSong instances did not have the "real" URI (the mapped path).

There was quite a lot of duplicate code for loading DetachedSong
objects, with different semantics for "securely" loading local files.

Reduce bloat.

This has been verified already in the caller.

Allows applying map_to_relative_path() with base_uri.

No caller passes a database song to this function, but if he does,
this check doesn't make sense.

This didn't make sense.

Detach the Song class completely from the public API, only to be used
by SimpleDatabase and the update thread.

Don't create an intermediate Song instance when all we want is a
DetachedSong.