Feature/connection state (#25)

* (cmake) add a warning about 32/64 conversion problems.

* fix typo

* New connection state for server code + fix OpenSSL double init bug

* update README

ixwebsocket/IXSocketOpenSSL.cpp

@@ -21,6 +21,7 @@
 namespace ix
 {
     std::atomic<bool> SocketOpenSSL::_openSSLInitializationSuccessful(false);
+    std::once_flag SocketOpenSSL::_openSSLInitFlag;
 
     SocketOpenSSL::SocketOpenSSL(int fd) : Socket(fd),
         _ssl_connection(nullptr),