Fix MessageBody::prepare in OptionsRequest and ReadyResponse where 0 bytes are allocated.
Fix potential crash in Session::execute(MessageBody* statement)

In Session::execute(MessageBody* statement), request_handler could possibly be deleted between execute(request_handler) and return request_handler->future(). A valid future could not then be returned. The future to be returned should be saved before the executing the request_handler.
Fixes for various memory issues
Merge branch 'planetbeing-1.0' into 1.0