This is no longer necessary with the new API.

As a side effect, the input plugin closes the SMB/CIFS connection
after closing the file.

This solves one part of
https://github.com/MusicPlayerDaemon/MPD/issues/916

[[maybe_unused]] (introduced in C++17) is standard C++.

https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
says that this is equivalent to the GNU unused attribute.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Introduced in C++17. It replaces gcc's warn_unused_result.

Found with modernize-use-nodiscard.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Just like std::condition_variable, which however has no way to specify
the std::mutex directly.

There is already one call in ReadServers(), which is the correct place
to do it.

There is already one call in ReadServers(), which is the correct place
to do it.

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.

We can remove those C++11 and C++14 kludges because we require GCC 4.9
now.

This eliminates some overhead, because the compiler doesn't need to
consider these functions throwing.

The old struct config_param remains only for top-level string options.