Improve index AMs' opclass validation procedures.

The amvalidate functions added in commit 65c5fcd353 were on the
crude side.  Improve them in a few ways:

* Perform signature checking for operators and support functions.

* Apply more thorough checks for missing operators and functions,
where possible.

* Instead of reporting problems as ERRORs, report most problems as INFO
messages and make the amvalidate function return FALSE.  This allows
more than one problem to be discovered per run.

* Report object names rather than OIDs, and work a bit harder on making
the messages understandable.

Also, remove a few more opr_sanity regression test queries that are
now superseded by the amvalidate checks.

src/include/access/amvalidate.h

@@ -0,0 +1,36 @@
+/*-------------------------------------------------------------------------
+ *
+ * amvalidate.h
+ *	  Support routines for index access methods' amvalidate functions.
+ *
+ * Copyright (c) 2016, PostgreSQL Global Development Group
+ *
+ * src/include/access/amvalidate.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef AMVALIDATE_H
+#define AMVALIDATE_H
+
+#include "utils/catcache.h"
+
+
+/* Struct returned (in a list) by identify_opfamily_groups() */
+typedef struct OpFamilyOpFuncGroup
+{
+	Oid			lefttype;		/* amoplefttype/amproclefttype */
+	Oid			righttype;		/* amoprighttype/amprocrighttype */
+	uint64		operatorset;	/* bitmask of operators with these types */
+	uint64		functionset;	/* bitmask of support funcs with these types */
+} OpFamilyOpFuncGroup;
+
+
+/* Functions in access/index/amvalidate.c */
+extern List *identify_opfamily_groups(CatCList *oprlist, CatCList *proclist);
+extern bool check_amproc_signature(Oid funcid, Oid restype, bool exact,
+					   int minargs, int maxargs,...);
+extern bool check_amop_signature(Oid opno, Oid restype,
+					 Oid lefttype, Oid righttype);
+extern bool opfamily_can_sort_type(Oid opfamilyoid, Oid datatypeoid);
+
+#endif   /* AMVALIDATE_H */