Promote certificate-related ctrl macros to functions.

Also document them in the process. Almost done!

BUG=404754

Change-Id: I3333c7e9ea6b4a4844f1cfd02bff8b5161b16143
Reviewed-on: https://boringssl-review.googlesource.com/5355
Reviewed-by: Adam Langley <agl@google.com>
3 files changed