Incidental cleanup of matviews code.

Move checking for unscannable matviews into ExecOpenScanRelation, which is
a better place for it first because the open relation is already available
(saving a relcache lookup cycle), and second because this eliminates the
problem of telling the difference between rangetable entries that will or
will not be scanned by the query.  In particular we can get rid of the
not-terribly-well-thought-out-or-implemented isResultRel field that the
initial matviews patch added to RangeTblEntry.

Also get rid of entirely unnecessary scannability check in the rewriter,
and a bogus decision about whether RefreshMatViewStmt requires a parse-time
snapshot.

catversion bump due to removal of a RangeTblEntry field, which changes
stored rules.

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201304151
+#define CATALOG_VERSION_NO	201304271
 
 #endif

src/include/executor/executor.h

@@ -341,7 +341,7 @@ extern void ExecAssignScanTypeFromOuterPlan(ScanState *scanstate);
 
 extern bool ExecRelationIsTargetRelation(EState *estate, Index scanrelid);
 
-extern Relation ExecOpenScanRelation(EState *estate, Index scanrelid);
+extern Relation ExecOpenScanRelation(EState *estate, Index scanrelid, int eflags);
 extern void ExecCloseScanRelation(Relation scanrel);
 
 extern void ExecOpenIndices(ResultRelInfo *resultRelInfo);

src/include/nodes/parsenodes.h

@@ -713,7 +713,6 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
-	bool		isResultRel;	/* used in target of SELECT INTO or similar */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
@@ -2461,7 +2460,7 @@ typedef struct CreateTableAsStmt
 	NodeTag		type;
 	Node	   *query;			/* the query (see comments above) */
 	IntoClause *into;			/* destination table */
-	ObjectType	relkind;		/* type of object */
+	ObjectType	relkind;		/* OBJECT_TABLE or OBJECT_MATVIEW */
 	bool		is_select_into; /* it was written as SELECT INTO */
 } CreateTableAsStmt;