Add a workaround for MSVC secure iterator problem where allowing the

destruction of an iterator to an already-destroyed string object results in
a program crash. Revert previous change to destroy buffers prior to
invoking the handler since it didn't fix the problem and wasn't cleaning
up all copies of the buffers anyway.


[SVN r41059]

libs/asio

@@ -1 +1 @@
-Subproject commit 970375748c3ddaeff7fdb8172b3490cb982d06c6
+Subproject commit 45add4d11ed508d58de89b8fdeba2eceb98bfa3f