Re: Add support for base64url variant

["Pierre Téchoueyres" <pierre.techoueyres@free.fr>]

Hello Eli,
> 
> Thanks, but please avoid posting such large patches as long as you
> don't have a copyright assignment for Emacs on file.

I have already signed paperwork for TRAMP and, I think, for Emacs.
But maybe there is something wrong with them ?

>  That's because
> just by reading the patch, people will remember some of the
> implementation, and will then have hard time to come up with a
> different one, should your copyright assignment paperwork not come
> through.
> 
> If you'd like to sign the forms, I will send them to you.  Then we
> could revisit the patch when the legal paperwork is done.

If you can't find my previous assignment, then yes send me them back.

> Thanks again for working on this.
Hope this could help.

I would like to have some discussion on how to improve some points :
- Is adding parameter to existing functions the way to go or is it 
better to add new ones for base64url
- I would like to improve base64-decode* in a way it could detect the 
variant but actually don't know how to do that.
- The documentations is not really what I would like to see (and there 
my English is faulty)

Thanks in advance.  Pierre.