pgsql: Add comment about COMMENT ON DATABASE failing for

Log Message:
-----------
Add comment about COMMENT ON DATABASE failing for differently-named
databases.

Modified Files:
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pgsql/src/bin/pg_dump:
pg_dump.c (r1.477 -> r1.478)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dump.c?r1=1.477&r2=1.478)