New async_result with two template parameters.
This change makes async_result consistent with the networking TS.
The older single-parameter form of async_result, and the handler_type
trait, have been deprecated. They have been retained for backwards
compatibility, and existing specialisations of these traits will still
be used. However, asynchronous operations that use the older form of
async_result/handler_type will not interoperate with completion tokens
that specialize only the new two-parameter async_result. For this
reason, the completion token types implemented by asio continue to
provide specialisations of the older form of async_result and
handler_type.
58 files changed
