This was done by running:

  ./fuzz/cert -merge=1 ../fuzz/cert_corpus ~/openssl/fuzz/corpora/x509

I bumped the max_len while doing so because some of those are rather
large.

Change-Id: Ic2caa09d5ff9ab05b46363940a91a03f270cbad8
Reviewed-on: https://boringssl-review.googlesource.com/12682
Reviewed-by: Adam Langley <agl@google.com>