alternative no anonymous enums

Anonymous enums play havoc with documentation;
there's no name to refer to. It may be that all
enums may either be named or replaced with constexpr
without breaking anything. Try replacing all
anonymous enums in include/core to see what happens.

This names SkCanvas::SaveLayerFlagsSet but leaves
SkCanvas::SaveLayerFlags as a uint32_t, to reduce
risk as compared to review.skia.org/123584.

There's also some chance that external linkage will
break if some client refers to anonymous enum in a way
that could require its address: see
https://stackoverflow.com/questions/22867654/enum-vs-constexpr-for-actual-static-constants-inside-classes
(This CL does not require definitions + declarations)

Brought bookmaker docs in line with this change.
This also tripped over missing code in bookmaker
handling constexpr so added that as well.

R=reed@google.com,bsalomon@google.com

Docs-Preview: https://skia.org/?cl=123920
Docs-Preview: https://skia.org/?cl=123584
Bug: skia:6898
Change-Id: I14a342edcfd59e139ef9e4501f562417c4c60391
Reviewed-on: https://skia-review.googlesource.com/123920
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Cary Clark <caryclark@skia.org>

0 files changed, 0 insertions, 0 deletions