Merge from trunk...

Fix compile error in regex overload of async_read_until.hpp. Fixes #5688

Explicitly specify the signal() function from the global namespace. Fixes #5722

Don't read the clock unless the heap is non-empty.

Change the SSL buffers sizes so that they're large enough to hold a complete TLS record. Fixes #5854

Make sure the synchronous null_buffers operations obey the user's non_blocking setting. Fixes #5756

Set size of select fd_set at runtime when using Windows.

Disable warning due to const qualifier being applied to function type.

Fix crash due to gcc_x86_fenced_block that shows up when using the Intel C++ compiler. Fixes #5763

Specialise operations for buffer sequences that are arrays of exactly two buffers.

Initialise all OpenSSL algorithms.

Fix error mapping when session is gracefully shut down.

Various performance improvements:

* Split the task_io_service's run and poll code.

* Use thread-local operation queues in single-threaded use cases (i.e. concurrency_hint is 1) to eliminate a lock/unlock pair.

* Only fence block exit when a handler is being run directly out of the io_service.

* Prefer x86 mfence-based fenced block when available.

* Use a plain ol' long for the atomic_count when all thread support is disabled.

* Allow some epoll_reactor speculative operations to be performed without holding the lock.

* Improve locality of reference by performing an epoll_reactor's I/O operation immediately before the corresponding handler is called. This also improves scalability across CPUs when multiple threads are running the io_service.

* Pass same error_code variable through to each operation's complete() function.

* Optimise creation of and access to the io_service implementation.

Remove unused state in HTTP server examples.

Add latency test programs.


[SVN r74863]

libs/asio

@@ -1 +1 @@
-Subproject commit 18a48222edeef468b6f5cb0663e687fda9123657
+Subproject commit 77dec8e703e41a1981cc45ca32bc97b57223f655