The rpmtsCallback() needs to be eliminated

The rpmtsCallback() used for progress/status communication
was originally intended to feed CPU cycles to a GUI installer.

As additional applications -- particularly bindings -- have
been written, there are complex side-effects driven by
events sent from the synchronous (i.e. rpm lib ceases to
run) events delivered through the callback.

Meanwhile the main functions of rpmtsCallback() are quite simple:
    pushing progress bars
    delivering state information (like what pkg is installed)
 that could be done by sharing a state structure instead.

The more complex operations of error handling SHOULD be done
through an exception framework, not as events delivered through
a synchronous callback mechanism.