Regenerate documentation.
Revision history.
Detection of boost 1.52 and 1.53.
asio version 1.8.3 released
Enable handler type requirements static_assert on clang.
Add new traits classes, handler_type and async_result, that allow
the customisation of the return type of an initiating function.
Add the asio::spawn() function, a high-level wrapper for running
stackful coroutines. It is based on the Boost.Coroutine library.

Here is an example of its use:

  asio::spawn(my_strand, do_echo);

  // ...

  void do_echo(asio::yield_context yield)
  {
    try
    {
      char data[128];
      for (;;)
      {
        std::size_t length =
          my_socket.async_read_some(
            asio::buffer(data), yield);

        asio::async_write(my_socket,
            asio::buffer(data, length), yield);
      }
    }
    catch (std::exception& e)
    {
      // ...
    }
  }

The first argument to asio::spawn() may be a strand, io_service or
completion handler. This argument determines the context in which the
coroutine is permitted to execute. For example, a server's per-client
object may consist of multiple coroutines; they should all run on the
same strand so that no explicit synchronisation is required.

The second argument is a function object with signature (**):

  void coroutine(asio::yield_context yield);

that specifies the code to be run as part of the coroutine. The
parameter yield may be passed to an asynchronous operation in place of
the completion handler, as in:

  std::size_t length =
    my_socket.async_read_some(
      asio::buffer(data), yield);

This starts the asynchronous operation and suspends the coroutine. The
coroutine will be resumed automatically when the asynchronous operation
completes.

Where a completion handler signature has the form:

  void handler(error_code ec, result_type result);

the initiating function returns the result_type. In the async_read_some
example above, this is std::size_t. If the asynchronous operation fails,
the error_code is converted into a system_error exception and thrown.

Where a completion handler signature has the form:

  void handler(error_code ec);

the initiating function returns void. As above, an error is passed back
in the future as a system_error exception.

To collect the error_code from an operation, rather than have it throw
an exception, associate the output variable with the yield_context as
follows:

  error_code ec;
  std::size_t length =
    my_socket.async_read_some(
      asio::buffer(data), yield[ec]);

**Note: if asio::spawn() is used with a custom completion handler of
type Handler, the function object signature is actually:

  void coroutine(asio::basic_yield_context<Handler> yield);
Move existing examples into a C++03-specific directory, and add a new
directory for C++11-specific examples.

A limited subset of the C++03 examples have been converted to their
C++11 equivalents. The generated documentation will include a diff
between the two.
Add the asio::use_future special value, which adds first-class support
for returning a C++11 std::future from an asynchronous operation's
initiating function.

To use asio::use_future, pass it to an asynchronous operation instead of
a normal completion handler. For example:

  std::future<std::size_t> length =
    my_socket.async_read_some(my_buffer, asio::use_future);

Where a completion handler signature has the form:

  void handler(error_code ec, result_type result);

the initiating function returns a std::future templated on result_type.
In the above example, this is std::size_t. If the asynchronous operation
fails, the error_code is converted into a system_error exception and
passed back to the caller through the future.

Where a completion handler signature has the form:

  void handler(error_code ec);

the initiating function returns std::future<void>. As above, an error
is passed back in the future as a system_error exception.
Regenerate documentation.