[MERGE/RFC] case sensitivity on Windows

[Mark Hammond]

> Mark Hammond wrote:
> 
> > I believe I've addressed every other comment in the attached patch.
> 
> Thanks for the improved implementation inside builtins.py. With changes
> like this, I'm never quite sure we've got every spot necessary but it
> certainly now feels (to me) like a safe step forward.
> 
> bb:tweak

Thanks again, but I must admit I'm finding the patch-ping-pong somewhat tedious.  The only substantive change relates to the doc build process, and I'm not familiar enough with that to ensure I won't get it wrong another time.

As this, and the setup.py patch are both sitting at "tweak" with very minor issues, I'll hope someone with submit permissions chooses to help out and land what they find appropriate.

Cheers,

Mark