small net cleanup

- add comment for disabling sigpipe
- add closing comment in compat.h
- remove redundant check in net.h

src/netbase.cpp

@@ -334,6 +334,7 @@ bool static ConnectSocketDirectly(const CService &addrConnect, SOCKET& hSocketRe
 
 #ifdef SO_NOSIGPIPE
     int set = 1;
+    // Different way of disabling SIGPIPE on BSD
     setsockopt(hSocket, SOL_SOCKET, SO_NOSIGPIPE, (void*)&set, sizeof(int));
 #endif