networkd: remove duplicate macro definitions
update TODO
networkd: update logging macros for parameter order, and errno, to match rest of the code
log: fix order of log_unit_struct() to match other logging calls

Also, while we are at it, introduce some syntactic sugar for creating
ERRNO= and MESSAGE= structured logging fields.
log: allow negative errno values

sd_bus_error_set_errno() allows negative errors too, hence, be equally
nice.
sd-bus: the attach_mask kernel module parameter is 64bit now, hence initialize it as such
core: only override kdbus attach mask when running as PID 1
log: also set errno to the passed error code before processing format string in log_struct()

That way the caller may use %m to print the specified error.
log: make socket address structs static const
log: change log_xyz_errno() calls to always return the negative error

This enables us to write things like this:

    int open_some_file(void) {

            fd = open("/dev/foobar", O_RDWR|O_CLOEXEC);
            if (fd < 0)
                    return log_error_errno(errno, "Failed to reboot: %m");

            return fd;
    }

Which is function that returns -errno on failure, as well as printing an
error message, all in one line.
kdbus: when running in a container, don't complain that we cannot write to /sys
update TODO