Rename pg_complete_relation_size() to pg_total_relation_size(), for the

sake of brevity and clarity.

Make pg_reload_conf(), pg_rotate_logfile(), and pg_cancel_backend()
return a boolean rather than an integer to indicate success or failure.

Along the way, make some minor cleanups to dbsize.c -- in particular,
use elog() rather than ereport() for "shouldn't happen" error
conditions, and remove some of the more flagrant violations of the
Postgres indentation conventions.

Catalog version bumped.