some post curve-fit refactoring

 - spin off LinearAlgebra.{c,h}
 - rename the rest of skcms_internal.h to TransferFunction.h
 - fold through powf/logf
 - do a little ?.f -> ?.0f for my sanity
 - slight formatting and API tweaks

Change-Id: I4756485f65650a539077f88ab6ea643d3da9d664
Reviewed-on: https://skia-review.googlesource.com/102181
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
7 files changed