Loosen dependency on boost about websocketpp

[zaphoyd]

Every Boost library that WebSocket++ uses is exclusively as a polyfill for the associated std library (or standalone Asio in the case of boost::asio). If you are using a well known C++11 or later compiler the library should autodetect the presence of std::thread, std::regex, etc. If you are using something more exotic there are preprocessor defines you can set to force the use of the std libraries.

It isn't super well documented, but look at common/cpp11.hpp for some more details and discussion.

In general, _WEBSOCKETPP_CPP11_STL_ will try to enable all std dependencies. There are other defines to swap specific dependencies between boost and std. I would recommend using all std dependencies unless the needed libraries are not avaliable in your version of the standard library.

[zaphoyd]

as an aside that might also be of interest for microcontrollers: It is possible to disable the use of exceptions (some embedded environments don't have), compression (which adds the zlib dependency), TLS support (which adds OpenSSL dependency), and the generation of cryptographically secure random numbers (boost/std <random> dependency). The latter two come with significant security and/or interoperability consequences, but have occasionally been useful in resource constrained environments.

[MartyMcFlyInTheSky]

I'm using C++20 so it sounds like I could drop all the dependencies from boost (except for standalone asio). For embedded systems it could be useful to include support for the widely adopted mbedtls library. Otherwise users are forced to create OpenSSL wrappers themselves. In any case, I'm looking into it a bit more, thank you!