Mark pg_stat_reset_shared as strict

This is the proper fix for bug #6082 about
pg_stat_reset_shared(NULL) causing a crash, and it reverts
commit 79aa4453 on head.

The workaround of throwing an error from inside the function is
left on backbranches (including 9.1) since this change requires
a new initdb.

src/backend/utils/adt/pgstatfuncs.c

@@ -1537,17 +1537,9 @@ pg_stat_reset(PG_FUNCTION_ARGS)
 Datum
 pg_stat_reset_shared(PG_FUNCTION_ARGS)
 {
-	if (PG_ARGISNULL(0))
-		/*
-		 * Same error message as in pgstat_reset_shared_counters(),
-		 * to keep translations the same.
-		 */
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("unrecognized reset target: \"%s\"", "null"),
-				 errhint("Target must be \"bgwriter\".")));
+	char	   *target = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
-	pgstat_reset_shared_counters(text_to_cstring(PG_GETARG_TEXT_PP(0)));
+	pgstat_reset_shared_counters(target);
 
 	PG_RETURN_VOID();
 }

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201106211
+#define CATALOG_VERSION_NO	201107031
 
 #endif

src/include/catalog/pg_proc.h

@@ -2663,7 +2663,7 @@ DATA(insert OID = 2230 (  pg_stat_clear_snapshot		PGNSP PGUID 12 1 0 0 0 f f f f
 DESCR("statistics: discard current transaction's statistics snapshot");
 DATA(insert OID = 2274 (  pg_stat_reset					PGNSP PGUID 12 1 0 0 0 f f f f f v 0 0 2278 "" _null_ _null_ _null_ _null_	pg_stat_reset _null_ _null_ _null_ ));
 DESCR("statistics: reset collected statistics for current database");
-DATA(insert OID = 3775 (  pg_stat_reset_shared			PGNSP PGUID 12 1 0 0 0 f f f f f v 1 0 2278 "25" _null_ _null_ _null_ _null_	pg_stat_reset_shared _null_ _null_ _null_ ));
+DATA(insert OID = 3775 (  pg_stat_reset_shared			PGNSP PGUID 12 1 0 0 0 f f f t f v 1 0 2278 "25" _null_ _null_ _null_ _null_	pg_stat_reset_shared _null_ _null_ _null_ ));
 DESCR("statistics: reset collected statistics shared across the cluster");
 DATA(insert OID = 3776 (  pg_stat_reset_single_table_counters	PGNSP PGUID 12 1 0 0 0 f f f f f v 1 0 2278 "26" _null_ _null_ _null_ _null_	pg_stat_reset_single_table_counters _null_ _null_ _null_ ));
 DESCR("statistics: reset collected statistics for a single table or index in the current database");