Revert "Revert "Merge to upstream r304942.""

This reverts commit 38a0d5af7e.

Test: make checkbuild
Test: ./run_tests.py
Test: ./run_tests.py --bitness 64

test/std/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/copy_move.pass.cpp

@@ -11,7 +11,8 @@
 
 // class function<R(ArgTypes...)>
 
-// function(const function& f);
+// function(const function&  f);
+// function(const function&& f);
 
 #include <functional>
 #include <memory>

test/std/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.targ/target.pass.cpp

@@ -63,6 +63,7 @@ int main()
     assert(A::count == 1);
     assert(f.target<A>());
     assert(f.target<int(*)(int)>() == 0);
+    assert(f.target<int>() == nullptr);
     }
     assert(A::count == 0);
     {
@@ -70,6 +71,7 @@ int main()
     assert(A::count == 0);
     assert(f.target<int(*)(int)>());
     assert(f.target<A>() == 0);
+    assert(f.target<int>() == nullptr);
     }
     assert(A::count == 0);
     {
@@ -77,6 +79,7 @@ int main()
     assert(A::count == 1);
     assert(f.target<A>());
     assert(f.target<int(*)(int)>() == 0);
+    assert(f.target<int>() == nullptr);
     }
     assert(A::count == 0);
     {
@@ -84,6 +87,7 @@ int main()
     assert(A::count == 0);
     assert(f.target<int(*)(int)>());
     assert(f.target<A>() == 0);
+    assert(f.target<int>() == nullptr);
     }
     assert(A::count == 0);
 }