"DEFAULT" is a bad name - all it says is that it's the default value,
but it doesn't say what it means.  The name NOTICE mimics the syslog
level.

[[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>

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.

Calling dbus_shutdown() too early will break the "udisks2" neighbor
plugin.

This flag is never read.

Make valgrind happy.

Map LogLevel::INFO to G_LOG_LEVEL_INFO, and LogLevel::DEFAULT to
G_LOG_LEVEL_MESSAGE.  Now client connect/disconnect message are only
logged on log_level "secure".

Finally fixes the regression by commit c1f4f1fd.

Prepare to migrate away from GLib.  Currently, we're still using GLib
as a backend.

Migrate the remaining callers to FatalError().

Temporary hotfix until we have integrated avahi into our new event
loop.

Implement an event loop without GLib.