Set `EXTENDED_GLOB` in the python module

[jeffwidman]

This is needed to find python.

It is often already set because a user has the directory or completion module loaded before this, but that's not always true.

See extensive debugging / further explanation here: https://github.com/sorin-ionescu/prezto/issues/1949

This does not fully resolve that issue, as there's another enhancement that I'll put up as a separate PR.

[belak]

I’m just merging this - it’s small and I thought we already made this change!

[jeffwidman]

Thanks!

[jeffwidman]

We agreed on it, but no one ever shipped it, and now I need to work on some python, so have some extra motivation :-D