message_channel_test: fixed failing test
Created periodic_utils_test
PLAT-592: added "AsyncWriterSource", a class designed to handle the specifics and pecularities of asynchronous writing to file descriptors
PLAT-649: added a tcp client class
Merge branch 'PLAT-649_tcp-client' into http-client-ih

Conflicts:
	service/async_writer_source.h
	service/service.mk
TcpClient obsoletes ClientTcpSocket