Unallocate opaque.

in built-in.  fixed backslases in source for libpq.

Pointed out by: Erik Bertelsen <erik@sockdev.uni-c.dk>

* Wrote max(date) and min(date) aggregates
* Wrote operator "-" for date; date - date yields number of days
  difference
* Wrote operator+(date,int) and operator-(date,int); the int is the
  number of days.  Each operator returns a new date.


By: Tom Tromey <tromey@creche.cygnus.com>

Randy is submitting a more comprehensive patch :)

	Erik Bertelsen <erik@sockdev.uni-c.dk>

Pointed out by: Erik Bertelsen <erik@sockdev.uni-c.dk>

psql now returns error from queries and errors files, so ignore return code.

In particular, no more compiled-in default for PGDATA or LIBDIR.  Commands
that need them need either invocation options or environment variables.
PGPORT default is hardcoded as 5432, but overrideable with options or
environment variables.

Requested by Bryan

explicitly.

Changes:

        * Unique index capability works using the syntax 'create unique
          index'.

        * Duplicate OID's in the system tables are removed.  I put
          little scripts called 'duplicate_oids' and 'find_oid' in
          include/catalog that help to find and remove duplicate OID's.
          I also moved 'unused_oids' from backend/catalog to
          include/catalog, since it has to be in the same directory
          as the include files in order to work.

        * The backend tries converting the name of a function or aggregate
          to all lowercase if the original name given doesn't work (mostly
          for compatibility with ODBC).

        * You can 'SELECT NULL' to your heart's content.

        * I put my _bt_updateitem fix in instead, which uses
          _bt_insertonpg so that even if the new key is so big that
          the page has to be split, everything still works.

        * All literal references to system catalog OID's have been
          replaced with references to define'd constants from the catalog
          header files.

        * I added a couple of node copy functions.  I think this was a
          preliminary attempt to get rules to work.