Fix Cygwin compilation:

- Fix various incompatibilities and differences between Linux and Cygwin builds
- Make usrsctp an optional dependency
- Fix building without SSL
- Add new secure random bytes function, use it for websockets
- Switch to libsrtp2 v2.6.0 (currently latest release)
- Add patch that makes latest libsrtp2 build in latest Cygwin
- Add patch that makes srt build in latest Cygwin
- Correctly allow linking libsrtp2 and srt to local mbedtls version

src/controller/controller_statistics.cpp

@@ -1121,7 +1121,7 @@ void Controller::statOnDisconnect(size_t id){
     dataPage.init(userPageName, 1, false, false);
     if(dataPage){
       // Session likely crashed while it was running
-      dataPage.init(userPageName, 1, true);
+      dataPage.master = true;
       FAIL_MSG("Session '%s' got cancelled unexpectedly. Cleaning up the leftovers...", thisSessionId.c_str());
     }
     // Finally remove the session lock which was created on bootup of the session