Shift the asterisks in the documentation's prototypes such that they
are consistent among each other. Use the right side to match what is
used in source code.
Addendum to commit v209~82.
This is a recurring submission and includes corrections to:
- missing words, preposition choice.
- change of /lib to /usr/lib, because that is what most distros are
using as the system-wide location for systemd/udev files.
Instead of returning an enum of return codes, make them return error
codes like kdbus does internally.
Also, document this behaviour so that clients can stick to it.
(Also rework bus-control.c to always have to functions for dbus1 vs.
kernel implementation of the various calls.)
