Async websocket creates a large binary & object file

**Version of Boost 1.70 ( 1.73 too )**

Steps necessary to reproduce the problem
--------------

Build sample async ssl websocket example

https://www.boost.org/doc/libs/1_70_0/libs/beast/example/websocket/client/async-ssl/websocket_client_async_ssl.cpp

On Mac OS with clang,
This will produce a **release binary 6.3 MB**. This is not due to OpenSSL. You will see that **object file ( websocket_client_async_ssl.o ) is also 3.8 MB.**

And following statement contributes to shocking **3.1 MB** of it.

// Perform the websocket handshake
ws_.async_handshake(host_, "/",
beast::bind_front_handler(
&session::on_handshake,
shared_from_this()));

while sync version of same ( ws_.handshake ), contributes only 400 KB extra.

File size changes as below.
----------
1. Async ws-handshake - ( obj: 3.8 MB, exe: 6.3 MB )
2. No ws-handshake - ( obj: 0.5 MB, exe: 2.9 MB )
3. Sync ws-handshake - ( obj: 0.9 MB, exe: 3.2 MB )

SSL present in all of above case.

I checked some cases with latest boost version 1.73 also, no noticeable change in reduction. Probably it takes more.