Since the lager_format rewrite, ~p and ~w now have different behaviour
with regard to printing lists as strings.

Before this fix, the code assumed that processes without a registered
name omitted the {registered_name, X} tuple in the crash report. In
actual fact, process_info/2 returns [] when the process has no
registered name, so unregistered processes were being printed with a
"name" of "[]". This corrects the code to print the Pid in this case
instead.

The ~w formatting used before was not printing lists embedded in other
terms. This change uses trunc_io to print those terms safely and without
potentially introducing linebreaks (like ~p would)

az558