Recent update to "git daemon" tries to enable the socket-level
KEEPALIVE, but when it is spawned via inetd, the standard input
file descriptor may not necessarily be connected to a socket.
Suppress an ENOTSOCK error from setsockopt().
* ew/daemon-socket-keepalive:
Windows: add missing definition of ENOTSOCK
daemon: ignore ENOTSOCK from setsockopt