Change packaged_handler to aggregate packaged_task

[chriskohlhoff]

Forward the required calls (i.e. not all members) to the packaged_task member

[chriskohlhoff]

Applied in 6d495682bf9f1452b746f19e01dfcf5b1613f004.

[chriskohlhoff]

Pre-Lenexa Summary

[async.package.handler]

Previously the packaged_handler class publicly derived from std::packaged_task. It did this to add an allocator_type typedef and get_allocator member function.

In Cologne, people expressed their dislike for the use of public inheritance and suggested that packaged_handler should instead aggregate packaged_task and forward the necessary member functions.

The change was included in revision 5.