Fix up styling in libevent example

Make the code simpler to read and follow by fixing up line breaks and
comment decorations.

Change-Id: I9e320b8795cf59aa38a0ce79da69d6ee535f77af
Reviewed-on: http://review.couchbase.org/40922
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>