Solution: remove implementation. Frank Hartmann <soundart@gmx.net>,
the author, rejected our request to relicense under MPL2, so we
have to remove his copyrighted work.
Tweetnacl is not security-supported and could not be used in
production environments anyway, the supported backend is libsodium.
* Allow CMAKE to generate ws and wss transports
I guess there is little use of just ws transport, so by default
GnuTLS (and libsodium) are enabled
* cmake libzmq including wss transport (ubuntu 19.10 and ubuntu 19.10 + wsl 1.0)
test_security_fails (libsodium assert !?)
* updated relicense
* make external libs gnutls nss sodium optional
* #ifdef WSS classes and functions, build test*ws* only if correct libs are included, warning if libs not present
* make libsodium optional
* cmake fix tests TIPC transport
* clang-format pointed out a wrongly placed #ifdef
* GnuTLS before 3.6.7 is not safe
* msvc doesn't agree with strlen in array declaration, test_socks now at least compiles on windows
* windows: libsodium build fails, missing include dirs set by env var
* ws transport test only works when GnuTLS is found
* Fixed condition to use NSS / built in SHA1, so that test_ws_transport should now pass, also when GnuTLS is not found
