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/access/hash.h

@@ -6,7 +6,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: hash.h,v 1.4 1996/11/10 03:04:36 momjian Exp $
+ * $Id: hash.h,v 1.5 1996/11/13 20:50:31 scrappy Exp $
  *
  * NOTES
  *	modeled after Margo Seltzer's hash implementation for unix. 
@@ -255,7 +255,7 @@ extern void hashbuild(Relation heap, Relation index, int natts,
 	AttrNumber *attnum, IndexStrategy istrat, uint16 pcount,
 	Datum *params, FuncIndexInfo *finfo, PredInfo *predInfo);
 extern InsertIndexResult hashinsert(Relation rel, Datum *datum, char *nulls,
-				    ItemPointer ht_ctid);
+				    ItemPointer ht_ctid, bool is_update);
 extern char *hashgettuple(IndexScanDesc scan, ScanDirection dir);
 extern char *hashbeginscan(Relation rel, bool fromEnd, uint16 keysz,
 			   ScanKey scankey);