spin off Curve.[ch]

   - add Curve.[ch], move skcms_eval_curve() there
   - swap argument order of skcms_eval_curve()... much better

TODO:
   - lerp tables in skcms_eval_curve()?
   - implement skcms_ApproximatelyEqualCurves()

Change-Id: Iabb37f20b48e357133245b444d18b0e929b16991
Reviewed-on: https://skia-review.googlesource.com/128401
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: Mike Klein <mtklein@chromium.org>
Reviewed-by: Brian Osman <brianosman@google.com>
10 files changed