Get tests running with warnings. Fix warnings in headers and tests

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@228344 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/utilities/function.objects/bind/func.bind/func.bind.bind/invoke_lvalue.pass.cpp

@@ -276,6 +276,7 @@ test3()
     const auto f = bind(&TFENode::foo, _1, 0UL);
     const TFENode n = TFENode{};
     bool b = f(n);
+    assert(b);
 }
 
 int main()