Patch to fix exception safety in boost::asio::ip::tcp::acceptor::async_accept when running the epoll reactor.

----

Steps to recreate the patch:
1) Original boost sources in the directory: 
       packages\3rdParty\boost\<version>\src\original\boost_<version>\...
2) Modified sources in:
       packages\3rdParty\boost\<version>\src\patched\boost_<version>\...
3) Cygwin console, in folder: packages/3rdParty/boost/<version>/src
4) Patch generated as: 
   diff -Nru original patched > boost_asio_epoll_accept_exception_safety.patch
5) This note added to the patch file


diff -Nru original/boost_1_57_0/boost/asio/detail/impl/epoll_reactor.ipp patched/boost_1_57_0/boost/asio/detail/impl/epoll_reactor.ipp
--- original/boost_1_57_0/boost/asio/detail/impl/epoll_reactor.ipp	2014-10-17 15:49:08.000000000 -0700
+++ patched/boost_1_57_0/boost/asio/detail/impl/epoll_reactor.ipp	2015-11-26 00:54:02.486738000 -0800
@@ -569,7 +569,7 @@
 struct epoll_reactor::perform_io_cleanup_on_block_exit
 {
   explicit perform_io_cleanup_on_block_exit(epoll_reactor* r)
-    : reactor_(r), first_op_(0)
+    : reactor_(r), first_op_(0), compensate_work_finished(false)
   {
   }
 
@@ -586,7 +586,7 @@
       // the fact that the task_io_service will call work_finished() once we
       // return.
     }
-    else
+    else if( compensate_work_finished )
     {
       // No user-initiated operations have completed, so we need to compensate
       // for the work_finished() call that the task_io_service will make once
@@ -598,6 +598,7 @@
   epoll_reactor* reactor_;
   op_queue<operation> ops_;
   operation* first_op_;
+  bool compensate_work_finished;
 };
 
 epoll_reactor::descriptor_state::descriptor_state()
@@ -635,6 +636,7 @@
   // be posted for later by the io_cleanup object's destructor.
   io_cleanup.first_op_ = io_cleanup.ops_.front();
   io_cleanup.ops_.pop();
+  io_cleanup.compensate_work_finished = true;
   return io_cleanup.first_op_;
 }
 
diff -Nru original/boost_1_57_0/boost/asio/detail/task_io_service_operation.hpp patched/boost_1_57_0/boost/asio/detail/task_io_service_operation.hpp
--- original/boost_1_57_0/boost/asio/detail/task_io_service_operation.hpp	2014-10-17 15:49:08.000000000 -0700
+++ patched/boost_1_57_0/boost/asio/detail/task_io_service_operation.hpp	2015-11-26 00:54:12.975835400 -0800
@@ -40,7 +40,13 @@
 
   void destroy()
   {
-    func_(0, this, boost::system::error_code(), 0);
+    try
+    {
+      func_(0, this, boost::system::error_code(), 0);
+    }
+    catch(std::exception&)
+    {
+    }
   }
 
 protected: