Commit of a *MAJOR* patch from Dan McGuirk <djm@indirect.com>

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.

src/include/commands/defrem.h

@@ -6,7 +6,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: defrem.h,v 1.5 1996/11/10 03:04:49 momjian Exp $
+ * $Id: defrem.h,v 1.6 1996/11/13 20:51:18 scrappy Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -23,7 +23,9 @@ extern void DefineIndex(char *heapRelationName,
 			char *indexRelationName,
 			char *accessMethodName,
 			List *attributeList,
-			List *parameterList, Expr *predicate,
+			List *parameterList, 
+			bool unique,
+			Expr *predicate,
 			List *rangetable);
 extern void ExtendIndex(char *indexRelationName,
 			Expr *predicate,