Many classes required to support type-erasure of handlers and boost::asio
types are now obsolete, so these classes and files are removed:
HTTPClientType, FixedInputBuffer, PeerRole, socket_wrapper,
client_session, basic_url, abstract_socket, buffer_sequence, memory_buffer,
enable_wait_for_async, shared_handler, wrap_handler, streambuf,
ContentBodyBuffer, SSLContext, completion-handler based handshake detectors.
These structural changes are made:
* Some missing includes added to headers
* asio module directory flattened
* Remove all calls to setlocale to ensure that the global
locale is always C.
* Also replace beast::SystemStats::getNumCpus() with
std:🧵:hardware_concurrency()
* Rename unity files
* Move some modules to new subdirectories
* Remove obsolete Visual Studio project files
* Remove obsolete coding style and TODO list