For querying tags, the real song URI should be used, because if the
(display) URI is different, requesting it will not produce a usable
response. This is a theoretical problem because none of the existing
playlist plugins sets the real_uri.
This requires changing the URI comparison in playlist::TagModified().
Closes https://github.com/MusicPlayerDaemon/MPD/issues/1154
Since we switched from autotools to Meson in commit
94592c1406, 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.
