generate SkColor include

bookmaker can now generate SkColor.h
This required adding support for #define, typedef,
global constexpr, and fixing various bugs, like
forward declared structs between comments.

Docs-Preview: https://skia.org/?cl=131260
Bug: skia:6898
TBR=caryclark@google.com
Change-Id: I6bee0c6f5c3a6820b04472a318abde8a2523dbbb
Reviewed-on: https://skia-review.googlesource.com/131260
Reviewed-by: Cary Clark <caryclark@skia.org>
Commit-Queue: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
12 files changed