Sync version number with release branch.
Remove dependency on Boost.Preprocessor library.
Fix error in async_receive_from example.
Remove unused variable assignment.
Fix a regression where, on some platforms, errors from async_connect are not
correctly propagated through to the completion handler.
Remove unused parameters and member variables.
Fix nfds argument to select.
Fix a regression on Windows where multiple threads are running an io_service.
Fix typo in serial ports overview.
Ensure ssl::io_op::want_ member is initialised.
Fix a bug in handler tracking, where it was not correctly printing out some handler IDs.
Fix comparison used to test for a successful synchronous accept.
Ensure signal number is correctly passed to the completion handler when
starting an async_wait on a signal that is already raised.
Suppress g++ 4.8+ warning about unused typedefs.
Fix link to refer to native_handle() rather than the deprecated native() function.
Enable the move optimisation (and otherwise eliminate a copy) for handlers
using the default invocation hook.
Clarify that programs must not issue overlapping async_write_at operations.
Fix error in comment.
Remove spurious whitespace.
Clean up some internal forward declarations.