Fix bug on Windows where certain operations might generate an error_code with
an invalid (i.e. NULL) error_category.

asio/include/asio/detail/impl/win_iocp_io_service.ipp

diff --git a/asio/include/asio/detail/impl/win_iocp_io_service.ipp b/asio/include/asio/detail/impl/win_iocp_io_service.ipp
index bb107db..250caae 100644
--- a/asio/include/asio/detail/impl/win_iocp_io_service.ipp
+++ b/asio/include/asio/detail/impl/win_iocp_io_service.ipp
@@ -235,8 +235,7 @@
   op->ready_ = 1;
 
   // Enqueue the operation on the I/O completion port.
-  if (!::PostQueuedCompletionStatus(iocp_.handle,
-        0, overlapped_contains_result, op))
+  if (!::PostQueuedCompletionStatus(iocp_.handle, 0, 0, op))
   {
     // Out of resources. Put on completed queue instead.
     mutex::scoped_lock lock(dispatch_mutex_);
@@ -256,8 +255,7 @@
     op->ready_ = 1;
 
     // Enqueue the operation on the I/O completion port.
-    if (!::PostQueuedCompletionStatus(iocp_.handle,
-          0, overlapped_contains_result, op))
+    if (!::PostQueuedCompletionStatus(iocp_.handle, 0, 0, op))
     {
       // Out of resources. Put on completed queue instead.
       mutex::scoped_lock lock(dispatch_mutex_);
@@ -284,8 +282,7 @@
   if (::InterlockedCompareExchange(&op->ready_, 1, 0) == 1)
   {
     // Enqueue the operation on the I/O completion port.
-    if (!::PostQueuedCompletionStatus(iocp_.handle,
-          0, overlapped_contains_result, op))
+    if (!::PostQueuedCompletionStatus(iocp_.handle, 0, 0, op))
     {
       // Out of resources. Put on completed queue instead.
       mutex::scoped_lock lock(dispatch_mutex_);