Fix deprecation notices in Mountain Lion

[ernie]

@alloy: This is a "works for me" fix for the deprecation notices. As mentioned in my comment on #62, you'll want to make sure I am using the right rects for the updated API.

Thanks for all your work on this fork on MacVim. Much appreciated. :)

[alloy]

@ernie I used a slightly different method and did not update the one in MMAtsuiTextView.m because that’s only used on OS X < 10.5, which is why, I suspect, @b4winckler didn’t update it upstream either.

Thanks!

[ernie]

@alloy yowza. Much nicer. I'd seen some advice not to use setFlipped somewhere, so I didn't do so. Much, much cleaner though. :)