Extend r-tree operator classes to handle Y-direction tests equivalent

to the existing X-direction tests.  An rtree class now includes 4 actual
2-D tests, 4 1-D X-direction tests, and 4 1-D Y-direction tests.
This involved adding four new Y-direction test operators for each of
box and polygon; I followed the PostGIS project's lead as to the names
of these operators.
NON BACKWARDS COMPATIBLE CHANGE: the poly_overleft (&<) and poly_overright
(&>) operators now have semantics comparable to box_overleft and box_overright.
This is necessary to make r-tree indexes work correctly on polygons.
Also, I changed circle_left and circle_right to agree with box_left and
box_right --- formerly they allowed the boundaries to touch.  This isn't
actually essential given the lack of any r-tree opclass for circles, but
it seems best to sync all the definitions while we are at it.

src/include/access/rtree.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/rtree.h,v 1.40 2005/06/24 00:18:52 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/access/rtree.h,v 1.41 2005/06/24 20:53:31 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,7 +21,7 @@
 #include "utils/rel.h"
 
 /* see rtstrat.c for what all this is about */
-#define RTNStrategies					8
+#define RTNStrategies					12
 #define RTLeftStrategyNumber			1
 #define RTOverLeftStrategyNumber		2
 #define RTOverlapStrategyNumber			3
@@ -30,6 +30,10 @@
 #define RTSameStrategyNumber			6
 #define RTContainsStrategyNumber		7
 #define RTContainedByStrategyNumber		8
+#define RTOverBelowStrategyNumber		9
+#define RTBelowStrategyNumber			10
+#define RTAboveStrategyNumber			11
+#define RTOverAboveStrategyNumber		12
 
 #define RTNProcs						3
 #define RT_UNION_PROC					1