Don't spew errors to the console whenever RPC gets disconnected. Fixes #163.

c++/src/capnp/rpc.c++

@@ -359,8 +359,17 @@ public:
     });
 
     // Indicate disconnect.
-    disconnectFulfiller->fulfill(DisconnectInfo {
-        connection.get<Connected>()->shutdown().attach(kj::mv(connection.get<Connected>())) });
+    auto shutdownPromise = connection.get<Connected>()->shutdown()
+        .attach(kj::mv(connection.get<Connected>()))
+        .then([]() -> kj::Promise<void> { return kj::READY_NOW; },
+              [](kj::Exception&& e) -> kj::Promise<void> {
+          // Don't report disconnects as an error.
+          if (e.getType() != kj::Exception::Type::DISCONNECTED) {
+            return kj::mv(e);
+          }
+          return kj::READY_NOW;
+        });
+    disconnectFulfiller->fulfill(DisconnectInfo { kj::mv(shutdownPromise) });
     connection.init<Disconnected>(kj::mv(networkException));
   }
 

c++/src/kj/debug.c++

@@ -80,6 +80,9 @@ Exception::Type typeOfErrno(int error) {
 #endif
       return Exception::Type::OVERLOADED;
 
+#ifdef ENOTCONN:
+    case ENOTCONN:
+#endif
 #ifdef ECONNABORTED
     case ECONNABORTED:
 #endif
@@ -120,6 +123,13 @@ Exception::Type typeOfErrno(int error) {
 #endif
 #if defined(EOPNOTSUPP) && EOPNOTSUPP != ENOTSUP
     case EOPNOTSUPP:
+#endif
+#ifdef ENOPROTOOPT
+    case ENOPROTOOPT:
+#endif
+#ifdef ENOTSOCK
+    // This is really saying "syscall not implemented for non-sockets".
+    case ENOTSOCK:
 #endif
       return Exception::Type::UNIMPLEMENTED;