They take a const pointer. See
http://llvm.org/docs/LibFuzzer.html#building

BUG=chromium:655016

Change-Id: Id6c7584c7a875e822b1fbff72163c888d02a9f44
Reviewed-on: https://boringssl-review.googlesource.com/11580
Reviewed-by: Steven Valdez <svaldez@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: Steven Valdez <svaldez@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>