[cairo] User-fonts landed

[Behdad Esfahbod]

Just pushed 40 commits, landing all the user-font stuff I had.  Will
look in the following issues in the coming days:

  - Documenting new API
  - Testing user-fonts using other fonts
  - Figuring out what to do with font options (non-AA, subpixel, metrics
hinting)
  - Peter's issues

That's all for now.  Review appreciated.

Cheers,
-- 
behdad
http://behdad.org/

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