memory leak in async_write

[DengrongWu <jeffreywu@…>]

First, call the function "async_write", when the callback function "HandleWriteRequest" is called, Then, close the socket.

Repeat the above operation, the memory will continue to increase.

In the attachment, you will see the demo. This program is running in the windows, the IDE is Microsoft visual studio 2008. Boost version is 1.45.0

Best regards.