Move strategy numbers to include/access/stratnum.h

For upcoming BRIN opclasses, it's convenient to have strategy numbers
defined in a single place.  Since there's nothing appropriate, create
it.  The StrategyNumber typedef now lives there, as well as existing
strategy numbers for B-trees (from skey.h) and R-tree-and-friends (from
gist.h).  skey.h is forced to include stratnum.h because of the
StrategyNumber typedef, but gist.h is not; extensions that currently
rely on gist.h for rtree strategy numbers might need to add a new

A few .c files can stop including skey.h and/or gist.h, which is a nice
side benefit.

Per discussion:
https://www.postgresql.org/message-id/20150514232132.GZ2523@alvh.no-ip.org

Authored by Emre Hasegeli and Álvaro.

(It's not clear to me why bootscanner.l has any #include lines at all.)

src/include/access/stratnum.h

@@ -0,0 +1,75 @@
+/*-------------------------------------------------------------------------
+ *
+ * stratnum.h
+ *	  POSTGRES strategy number definitions.
+ *
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/access/stratnum.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef STRATNUM_H
+#define STRATNUM_H
+
+/*
+ * Strategy numbers identify the semantics that particular operators have
+ * with respect to particular operator classes.  In some cases a strategy
+ * subtype (an OID) is used as further information.
+ */
+typedef uint16 StrategyNumber;
+
+#define InvalidStrategy ((StrategyNumber) 0)
+
+/*
+ * Strategy numbers for B-tree indexes.
+ */
+#define BTLessStrategyNumber			1
+#define BTLessEqualStrategyNumber		2
+#define BTEqualStrategyNumber			3
+#define BTGreaterEqualStrategyNumber	4
+#define BTGreaterStrategyNumber			5
+
+#define BTMaxStrategyNumber				5
+
+
+/*
+ * Strategy numbers common to (some) GiST, SP-GiST and BRIN opclasses.
+ *
+ * The first few of these come from the R-Tree indexing method (hence the
+ * names); the others have been added over time as they have been needed.
+ */
+#define RTLeftStrategyNumber			1		/* for << */
+#define RTOverLeftStrategyNumber		2		/* for &< */
+#define RTOverlapStrategyNumber			3		/* for && */
+#define RTOverRightStrategyNumber		4		/* for &> */
+#define RTRightStrategyNumber			5		/* for >> */
+#define RTSameStrategyNumber			6		/* for ~= */
+#define RTContainsStrategyNumber		7		/* for @> */
+#define RTContainedByStrategyNumber		8		/* for <@ */
+#define RTOverBelowStrategyNumber		9		/* for &<| */
+#define RTBelowStrategyNumber			10		/* for <<| */
+#define RTAboveStrategyNumber			11		/* for |>> */
+#define RTOverAboveStrategyNumber		12		/* for |&> */
+#define RTOldContainsStrategyNumber		13		/* for old spelling of @> */
+#define RTOldContainedByStrategyNumber	14		/* for old spelling of <@ */
+#define RTKNNSearchStrategyNumber		15		/* for <-> (distance) */
+#define RTContainsElemStrategyNumber	16		/* for range types @> elem */
+#define RTAdjacentStrategyNumber		17		/* for -|- */
+#define RTEqualStrategyNumber			18		/* for = */
+#define RTNotEqualStrategyNumber		19		/* for != */
+#define RTLessStrategyNumber			20		/* for < */
+#define RTLessEqualStrategyNumber		21		/* for <= */
+#define RTGreaterStrategyNumber			22		/* for > */
+#define RTGreaterEqualStrategyNumber	23		/* for >= */
+#define RTSubStrategyNumber				24		/* for inet >> */
+#define RTSubOrEqualStrategyNumber		25		/* for inet <<= */
+#define RTSuperStrategyNumber			26		/* for inet << */
+#define RTSuperOrEqualStrategyNumber	27		/* for inet >>= */
+
+#define RTMaxStrategyNumber				27
+
+
+#endif		/* STRATNUM_H */