Allow MessageBase::mark_sent to be overridden by derived classes
Allow MessageBase::mark_sent to be overridden by derived classes

buaasun/grappa,alexfrolov/grappa,alexfrolov/grappa,buaasun/grappa,uwsampa/grappa,alexfrolov/grappa,uwsampa/grappa,uwsampa/grappa,uwsampa/grappa,buaasun/grappa,buaasun/grappa,alexfrolov/grappa,alexfrolov/grappa,buaasun/grappa,uwsampa/grappa,buaasun/grappa,uwsampa/grappa,alexfrolov/grappa,alexfrolov/grappa,uwsampa/grappa,buaasun/grappa