remove unused parts of SkTypes.h

Lots of completely unused bits and bobs removed.

I've decided SK_SUPPORT_UNITTEST and its single use are not
very compelling.

tests/CPlusPlusEleven was the only user of Sk32ToBool(),
and no longer generally needed.

Change-Id: I3ee75560f1e1e1cf5ad89ee7df8d7694b5dffdb3
Reviewed-on: https://skia-review.googlesource.com/133622
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
9 files changed