sk_FOO_num may be called on const stacks. Given that was wrong, I suspect no
one ever uses a const STACK_OF(T)...

Other macros were correctly const, but were casting the constness a way (only
to have it come back again).

Also remove the extra newline after a group. It seems depending on which
version of clang-format was being used, we'd either lose or keep the extra
newline. The current file doesn't have them, so settle on that.

Change-Id: I19de6bc85b0a043d39c05ee3490321e9f0adec60
Reviewed-on: https://boringssl-review.googlesource.com/7946
Reviewed-by: Steven Valdez <svaldez@google.com>
Reviewed-by: David Benjamin <davidben@google.com>