[PATCH 1 of 2 STABLE] diffhelpers: add canstripcr=True to fix_newline

[Yuya Nishihara]

On Wed, 26 Apr 2017 11:33:46 -0700, Jun Wu wrote:
> Excerpts from Yuya Nishihara's message of 2017-04-26 20:39:30 +0900:
> > [...]
> > I have a patch set to get rid of the whole mess of pure/c-ext import hacks.
> > Hopefully the copy-paste will die in 4.3.
> 
> Ah, I may have written something similar [1] yesterday. I guess your patches
> may be cleaner as I didn't improve __init__.py.
> 
> [1]: https://bpaste.net/show/742e6c81af22

Basically I'm going to wrap a module by dualmod(cext, pure) so missing
attribute access will automatically fall back to a pure module. This wrapper
will be enabled only when the module policy is permissive.