helper function for test applications

[Colin Walters]

On Fri, Mar 12, 2010 at 10:02 AM, Colin Walters <walters at verbum.org> wrote:
>
> would be better. Having it always go to stderr is a little inflexible;
> this way an app author can more easily split things up into separate
> log files if they want, or even set up an internal pipe and filter the
> stream for targeted messages.  Also we shouldn't really be treating
> functions which start with _ as public.

Note also for extra credit, making the DBUS_VERBOSE environment
variable accept a string like "fd=2" would be cool.