document SkColor.h

SkColor.h uses #define liberally, and has many global symbols,
two things bookmaker hasn't seen in other includes.

Revised .h -> .bmh converter to work with SkColor.h as well
as updating how .bmh indices are built.

Generated SkColor_Reference.bmh for globals, and
SkColor4f_Reference.bmh for class.

Other than the existing comments, this doesn't update the
documentation or add new examples.

Docs-Preview: https://skia.org/?cl=118985
TBR=caryclark@google.com
Bug: skia:6898
Change-Id: I5978257ee0e51319823efbe8dfc467a08c99ffe0
Reviewed-on: https://skia-review.googlesource.com/118985
Commit-Queue: Cary Clark <caryclark@skia.org>
Reviewed-by: Cary Clark <caryclark@skia.org>
25 files changed