Creating backup files with ~ suffix can be undesirable in some environment,
such as when building RPM packages. Instead of requiring the user to remove
those files manually, option -n was added, that simply disables this feature.

-n was selected because 2to3 has the same option with this behavior.
(cherry picked from commit 5affd5c2)
Co-authored-by: Miro Hrončok <miro@hroncok.cz>