binwrite should pass write only when options are not empty but don't have a "mode"
IO.sysopen accepts mode & permission that are nil
Merge pull request #763 from josedonizetti/io_binwrite

binwrite should pass write only when options are not empty but don't have a "mode"
Merge pull request #766 from josedonizetti/sysopen_accepts_mode_and_permission_nil

IO.sysopen accepts mode & permission that are nil