Move symbols for ExecMergeJoin's state machine into nodeMergejoin.c.

There's no reason for these values to be known anywhere else.  After
doing this, executor/execdefs.h is vestigial and can be removed.

Author: tglsfdc

src/backend/executor/nodeMergejoin.c

@@ -95,7 +95,6 @@
 #include "access/nbtree.h"
 #include "catalog/pg_amop.h"
 #include "executor/execdebug.h"
-#include "executor/execdefs.h"
 #include "executor/nodeMergejoin.h"
 #include "miscadmin.h"
 #include "utils/acl.h"
@@ -104,6 +103,21 @@
 #include "utils/syscache.h"
 
 
+/*
+ * States of the ExecMergeJoin state machine
+ */
+#define EXEC_MJ_INITIALIZE_OUTER		1
+#define EXEC_MJ_INITIALIZE_INNER		2
+#define EXEC_MJ_JOINTUPLES				3
+#define EXEC_MJ_NEXTOUTER				4
+#define EXEC_MJ_TESTOUTER				5
+#define EXEC_MJ_NEXTINNER				6
+#define EXEC_MJ_SKIP_TEST				7
+#define EXEC_MJ_SKIPOUTER_ADVANCE		8
+#define EXEC_MJ_SKIPINNER_ADVANCE		9
+#define EXEC_MJ_ENDOUTER				10
+#define EXEC_MJ_ENDINNER				11
+
 /*
  * Runtime data for each mergejoin clause
  */

src/include/executor/execdefs.h

@@ -1425,7 +1425,7 @@ typedef struct NestLoopState
  *
  *		NumClauses		   number of mergejoinable join clauses
  *		Clauses			   info for each mergejoinable clause
- *		JoinState		   current "state" of join.  see execdefs.h
+ *		JoinState		   current state of ExecMergeJoin state machine
  *		ExtraMarks		   true to issue extra Mark operations on inner scan
  *		ConstFalseJoin	   true if we have a constant-false joinqual
  *		FillOuter		   true if should emit unjoined outer tuples anyway