extract GaussNewton.c

Use it to fit skcms_TF15, Ax^5 + Bx^4 + Cx^3 + Dx^2 + (1-A-B-C-D)x.

Change-Id: I069dbffaa589d7207d82b805e342605d1fed69fb
Reviewed-on: https://skia-review.googlesource.com/119009
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
31 files changed