Small changes to generic_endpoint and send_msg.

Want the return value of endpoint_send to be just like that of send.
Bug fix: socket handling across fork (take two).

Partial revert of previous code. The listener does the accept, then
closes the new socket (which is duplicated in the child). The child
closes the listener socket (duplicated in the parent). This should
solve the unclaimed descriptors problem.

TODO still don't seem to be correctly segmenting the connections...