Remove extraneous parens around return arguments.

This resolves #540.

test/stress/microbench.c

@@ -156,10 +156,10 @@ TEST_END
 
 int
 main(void) {
-	return (test(
+	return test(
 	    test_malloc_vs_mallocx,
 	    test_free_vs_dallocx,
 	    test_dallocx_vs_sdallocx,
 	    test_mus_vs_sallocx,
-	    test_sallocx_vs_nallocx));
+	    test_sallocx_vs_nallocx);
 }