multi-arch support for CGAL

[Joachim Reichel]

Dear maintainers of reverse dependencies of CGAL,

I just uploaded 4.5-3 to experimental which adds multi-arch support. I invite
you to test this version. I've successfully build all reverse dependencies (yade
failed for unrelated reasons), but did not test the generated binary packages.
This version is *not* meant for jessie, I plan to upload multi-arch support to
sid once jessie is released.

Best regards,
  Joachim