[MERGE] Fix how cog.py is invoked on Windows

[Mark Hammond]

> Bundle buggy isn't recognizing your patches, because of their naming
> and
> content type.
> 
> The following file extensions indicate patches: .patch .diff
> The following MIME types indicate patches: text/x-patch text/x-diff

The problem is that in the past, when I sent files with a .patch extension,
my email clients didn't set the content-type as a text file - so people
emailed me asking me to attach the patches with a .txt extension.  Which I
did.

It seems I'm damned if I do and damned if I don't :(

(And I'm aware my mail client isn't - um - "approved" - but it is what I
need to deal with and very common on Windows...  And its even likely that by
adjusting the content-type associated with ".patch" in my registry to be a
text file I could also make thing work as expected (which I did do on my
desktop machine - but I'm currently on my laptop and haven't jumped those
hoops yet - but the reality is that will be beyond many Windows users - as
will chastising them for having an incorrect content-type in their
attachments.

Mark