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/backend/utils/cache/catcache.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *    $Header: /cvsroot/pgsql/src/backend/utils/cache/catcache.c,v 1.4 1996/11/08 05:59:53 momjian Exp $
+ *    $Header: /cvsroot/pgsql/src/backend/utils/cache/catcache.c,v 1.5 1996/11/13 20:50:04 scrappy Exp $
  *
  * Notes:
  *	XXX This needs to use exception.h to handle recovery when
@@ -901,6 +901,7 @@ SearchSysCache(struct catcache *cache,
 	    sd =  heap_beginscan(relation, 0, NowTimeQual,
 				 cache->cc_nkeys, cache->cc_skey);
 	    
+	    /* should this buffer be ReleaseBuffer'd?  --djm 8/20/96 */
 	    ntp = heap_getnext(sd, 0, &buffer);
 	    
 	    MemoryContextSwitchTo((MemoryContext)CacheCxt);