libstdc++: Add dg-output to two tests

These tests are expected to run interactively, with the output checked
by eye. Nobody ever does that, but we can at least use dg-output to
check that the output is as expected.

libstdc++-v3/ChangeLog:

	* testsuite/27_io/objects/char/2.cc: Use dg-output.
	* testsuite/27_io/objects/wchar_t/2.cc: Use dg-output.

libstdc++-v3/testsuite/27_io/objects/char/2.cc

@@ -38,6 +38,8 @@ void test04()
   cout.flush();
 }
 
+// { dg-output "hello fine world" }
+
 int 
 main()
 {

libstdc++-v3/testsuite/27_io/objects/wchar_t/2.cc

@@ -38,6 +38,8 @@ void test04()
   wcout.flush();
 }
 
+// { dg-output "hello fine world" }
+
 int 
 main()
 {