Fix potential memory leak

Fix potential memory leak

- Got rid of ifdef _WIN32 stuff adn moved to plat_ files instead.
- Also, check all calls to lws_zalloc, was potential failure on WIN32
- Made context destory enable to destroy a half inited context as well. This way I got get rid of some of the error handling complexity in libwebsocket_create_context
- Added TODOs for some potential problems I see where things might be leaking and such