Bug: anonymous gen_event process + format_status.

[Geoff Cant]

Hi all, it seems during the last round of format_status improvements a
bug was introduced for anonymous gen_event processes.

Repro:
{ok, Pid} = gen_event:start(), sys:get_status(Pid).

Expected: Status report
Actual: Crash due to calling lists:concat on a list containing a pid()

I've done some work on format_status here:
git fetch git://github.com/archaelus/otp.git format_status_improvements

I've fixed the bug by porting the gen_fsm StatusHdr code into gen_event
at 00b032608c3ad3573d2b. Then I refactored the StatusHdr code out of
gen_server, gen_fsm and gen_event into 'gen' at 9103fa5136d360839aad,
and extended the test suite to test for the anon gen_event format status
bug at 480f1282d9bcdd7d40c3.

Cheers,
-- 
Geoff Cant