Use copy file range from sysx

Use pooled buffers for copy

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

fs/copy_windows.go

@@ -18,7 +18,9 @@ func copyFileInfo(fi os.FileInfo, name string) error {
 }
 
 func copyFileContent(dst, src *os.File) error {
-	_, err := io.Copy(dst, src)
+	buf := bufferPool.Get().([]byte)
+	_, err := io.CopyBuffer(dst, src, buf)
+	bufferPool.Put(buf)
 	return err
 }