Incorporate transpose-windows

[dgtized]

https://www.emacswiki.org/emacs/TransposeWindows

crux has swap-windows, which is for two windows only, and appears to require some special tricks around window-start and the like.

I've had it in my .config for years, and it's quite useful (particularly on larger displays), but otherwise only seems to be directly referenced in the emacs wiki. I'm happy to make a PR to pull it in, but wanted to check if anyone had ideas on how to handle attribution correctly. This package seems an appropriate place to bring it in, but it's definitely one of those snippets that's tricky to determine who wrote it originally, so not sure if that is a concern.

[bbatsov]

PR welcome.

This package seems an appropriate place to bring it in, but it's definitely one of those snippets that's tricky to determine who wrote it originally, so not sure if that is a concern.

I think that a simple comment will do. I definitely don't think this is a major concern. GPL is known as copyleft for a reason. :-)

[dgtized]

Addressed by #21 and #22.