Deprecating RULES

Not many RULE-lovers out there, once you've tried to use them.

Allowing RULEs complicates various things and can make security more difficult.

For 9.3, I suggest we create a DDL trigger by default which prevents
RULEs and throws an ERROR that explains they are now deprecated.

Anybody that really cares can delete this and use them. Sometime in
future, we hard code it, barring complaints.

Comments?

-- Simon Riggs                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services