Modify pg_dump to assume that a check constraint is inherited if its

Modify pg_dump to assume that a check constraint is inherited if its
name matches the name of any parent-table constraint, without looking
at the constraint text.  This is a not-very-bulletproof workaround for
the problem exhibited by Berend Tober last month.  We really ought to
record constraint inheritance status in pg_constraint, but it's looking
like that may not get done for 8.1 --- and even if it does, we will
need this kluge for dumping from older servers.