test suite updates: highlight failed test scripts; optionally save failed test output; report number of successful tests; exit based on number of test failures; indent warning messages to make them stand out

tests/set-e.right

@@ -35,6 +35,7 @@ b
 after 1
 a
 0
+	set-e1.sub
 non-posix foo
 after brace group failure: 1
 A 1
@@ -64,9 +65,11 @@ foo
 after failure 1
 after failure 2
 after failure 3
+	set-e2.sub
 true || false no exit
 false || true no exit
 false && false no exit
+	set-e3.sub
 A:
 B:
 ehB