re PR c++/53711 (Wunused-function should warn for functions in the unnamed namespace)

	PR c++/53711
	* d++.dg/warn/anonymous-namespace-6.C: New test.

From-SVN: r208569

gcc/testsuite/g++.dg/warn/anonymous-namespace-6.C

+// PR c++/53711
+// { dg-options -Wall }
+
+namespace {
+  void f () // { dg-warning "not used" }
+  {
+  }
+}