Victor fix for crashing protosharesd on Linux following fork -

The cause of this problem is that the old client disconnects the new client due to the wrong proof of work; however there is a race condition that sometimes the new client still wants to communicate with the old client, but since the old client has closed this connection, a "broken pipe" signal will be passed to the new client and it is terminated.

Interestingly, on Windows platform a flag MSG_NOSIGNAL is passed to send() to avoid this problem. This should also apply to Linux since MSG_NOSIGNAL is supported after kernel 2.2+