Add skcms_AdaptToXYZD50 to the API

This splits of the part inside skcms_PrimariesToXYZD50 which computes
the chromatic adaptation matrix into a new function
skcms_AdaptToXYZD50.

This is useful when creating an ICC profile, to convert values to D50
which ICC uses.

Change-Id: I2a453ee9f17f7173868bd8341ef793614dde01bb
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/259136
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
3 files changed