Add REPLICATION privilege for ROLEs

This privilege is required to do Streaming Replication, instead of
superuser, making it possible to set up a SR slave that doesn't
have write permissions on the master.

Superuser privileges do NOT override this check, so in order to
use the default superuser account for replication it must be
explicitly granted the REPLICATION permissions. This is backwards
incompatible change, in the interest of higher default security.

src/backend/utils/init/miscinit.c

@@ -231,6 +231,7 @@ static int	SecurityRestrictionContext = 0;
 static bool SetRoleIsActive = false;
 
 
+
 /*
  * GetUserId - get the current effective user ID.
  *
@@ -388,6 +389,24 @@ SetUserIdAndContext(Oid userid, bool sec_def_context)
 }
 
 
+/*
+ * Check if the authenticated user is a replication role
+ */
+bool
+is_authenticated_user_replication_role(void)
+{
+	bool            result = false;
+	HeapTuple       utup;
+
+	utup = SearchSysCache1(AUTHOID, ObjectIdGetDatum(AuthenticatedUserId));
+	if (HeapTupleIsValid(utup))
+	{
+		result = ((Form_pg_authid) GETSTRUCT(utup))->rolreplication;
+		ReleaseSysCache(utup);
+	}
+	return result;
+}
+
 /*
  * Initialize user identity during normal backend startup
  */