unicode font-backend + tiling

[Miles Bader]

I tried merging the current unicode branch with my tiling and lexbind
branches (mostly so I could get anti-aliased fonts using the new font
backend stuff).... I'm happy to report that there were only a few minor
problems, and generally it merged without incident.

Here's a screen shot with image backgrounds ("tiling") + anti-aliased
fonts:

   http://snogglethorpe.googlepages.com/emacs-unicodetilinglexbind-0.png

-Miles
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