Add missing test for -Wunneeded-member-functions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184371 91177308-0d34-0410-b5e6-96231b3b80d8

test/SemaCXX/warn-member-not-needed.cpp

+// RUN: %clang_cc1 -fsyntax-only -verify -Wunneeded-member-function %s
+
+namespace {
+  class A {
+    void g() {} // expected-warning {{is not needed and will not be emitted}}
+    template <typename T>
+    void foo() {
+      g();
+    }
+  };
+}