Revert commit removing allocator support from packaged_task. Will investigate further

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@319091 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/thread/futures/futures.task/futures.task.members/ctor2.fail.cpp

@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: libcpp-has-no-threads
+// UNSUPPORTED: c++98, c++03
+
+// <future>
+
+// class packaged_task<R(ArgTypes...)>
+// template <class F, class Allocator>
+//   packaged_task(allocator_arg_t, const Allocator& a, F&& f);
+// These constructors shall not participate in overload resolution if
+//    decay<F>::type is the same type as std::packaged_task<R(ArgTypes...)>.
+
+#include <future>
+#include <cassert>
+
+#include "test_allocator.h"
+
+struct A {};
+typedef std::packaged_task<A(int, char)> PT;
+typedef volatile std::packaged_task<A(int, char)> VPT;
+
+int main()
+{
+    PT p { std::allocator_arg_t{}, test_allocator<A>{}, VPT {}}; // expected-error {{no matching constructor for initialization of 'PT' (aka 'packaged_task<A (int, char)>')}}
+    // expected-note-re@future:* 1 {{candidate template ignored: {{(disabled by 'enable_if')|(requirement '.*' was not satisfied)}}}}
+}

test/std/thread/futures/futures.task/futures.task.members/ctor_func_alloc.pass.cpp

@@ -16,6 +16,9 @@
 
 // class packaged_task<R(ArgTypes...)>
 
+// template <class F, class Allocator>
+//     explicit packaged_task(allocator_arg_t, const Allocator& a, F&& f);
+
 #include <future>
 #include <cassert>