pg_stat_statements forgot to let previous occupant of hook get control too.

pgss_post_parse_analyze() neglected to pass the call on to any earlier
occupant of the post_parse_analyze_hook.  There are no other users of that
hook in contrib/, and most likely none in the wild either, so this is
probably just a latent bug.  But it's a bug nonetheless, so back-patch
to 9.2 where this code was introduced.