Duplicate constraint names in 7.0.3

Hi,

I have noticed that it is possible to create duplicate CHECK (haven't tried
other) constraints in 7.0.3 by doing something like this:

CREATE TABLE "test" (
"a" int4,
CHECK (a < 400),
CONSTRAINT "$1" CHECK (a > 5)
);

I was just fiddling around with trying to implement the 'DROP CONSTRAINT'
code (it's quite hard - don't wait up for me!) and it would seem to be a bad
thing that it's possible to have two constraints with the same name in a
table.

Surely there should be a UNIQUE (rcrelid, rcname) on pg_relcheck?, or at
least better checking in the CREATE TABLE code?

Chris