Log Message:
Update asio to 1.10.8

Asio 1.10.8

* Added compatibility with OpenSSL 1.1.0.

* Fixed out-of-bounds iterator use in `asio::connect()` when the
  `connect_condition` returns an end iterator.

* Added a workaround for a move detection problem on MSVC 2015 Update 2.

* Changed a workaround that was previously added for broken Windows firewalls
  to only bind to 127.0.0.1 if `getsockname` reports 0.0.0.0.

* Added call to `SSL_COMP_free_compression_methods` to fix two memory leaks
  reported at shutdown, for OpenSSL versions >= 1.0.2 and < 1.1.0.

* Fixed `use_future` compile error encountered on some standard library
  implementations, by changing `std::allocator<void>` use to a non-void
  template parameter.

* Enabled use of native `getaddrinfo` by default on Apple OSes, rather than
  emulation in terms of `getipnodebyname`.

Asio 1.10.7

* Added support for Windows 8.1 Store apps.

* Fixed macro multiple definition error on Microsoft Visual Studio 2015.

* Changed Asio's SSL wrapper to respect OpenSSL's `OPENSSL_NO_SSL3` feature
  test `#define`.

* Changed Asio's SSL wrapper to use OpenSSL's new `SSL_CTX_clear_chain_certs`
  function, if available.

* Suppressed a clang 3.6+ warning about unused typedefs.

* Regenerated certificates used by SSL examples.

* Fixed buffer sizes passed to `strncat` in the `getaddrinfo` emulation and in
  the SSL wrapper's password handling.

* Changed Windows backend to use non-macro `CreateEventW` rather than
  `CreateEvent`.