2 minor fixes to transferkeys, otherwise it was perfect 1st time!

Needed to send a trailing NUL to end a request, and set the read handle
non-blocking.

Also, set fileSystemEncoding on all handles, since there's a filename in
there.

Assistant/TransferrerPool.hs

@@ -62,6 +62,8 @@ mkTransferrer program = do
 	closeFd tread
 	myreadh <- fdToHandle myread
 	mywriteh <- fdToHandle mywrite
+	fileEncoding myreadh
+	fileEncoding mywriteh
 	return $ Transferrer
 		{ transferrerRead = myreadh
 		, transferrerWrite = mywriteh