for use by recently created macros.

Implement SET keyword = DEFAULT and SET TIME ZONE DEFAULT.
Re-enable JOIN= option in CREATE OPERATOR statement (damaged for v6.2).
Allow more SQL and/or Postgres reserved words as column identifiers
 or, if there are shift/reduce problems, at least as column labels.

Enable SET TIME ZONE using TZ environment variable.

Add istrue() and isfalse() routines to implement SQL3 IS TRUE and IS FALSE.

 This allows mixed-case identifiers if surrounded by double quotes.
Add mention of "with location" clause for "create database" in help.