rpc: add new client, use it everywhere

The new client implementation supports concurrent requests,
subscriptions and replaces the various ad hoc RPC clients
throughout go-ethereum.

rpc/ipc_unix.go

@@ -22,6 +22,8 @@ import (
 	"net"
 	"os"
 	"path/filepath"
+
+	"golang.org/x/net/context"
 )
 
 // ipcListen will create a Unix socket on the given endpoint.
@@ -40,6 +42,6 @@ func ipcListen(endpoint string) (net.Listener, error) {
 }
 
 // newIPCConnection will connect to a Unix socket on the given endpoint.
-func newIPCConnection(endpoint string) (net.Conn, error) {
-	return net.DialUnix("unix", nil, &net.UnixAddr{Name: endpoint, Net: "unix"})
+func newIPCConnection(ctx context.Context, endpoint string) (net.Conn, error) {
+	return dialContext(ctx, "unix", endpoint)
 }