Add basic BLAKE2b-256 support.

Our use-case for this does not require optimisation at the current time,
so a clean C implementation is fine.

Change-Id: I8f29572c33e8dbcc37961c099c71c14aafc8d0a3
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/45164
Reviewed-by: David Benjamin <davidben@google.com>

tool/speed.cc

diff --git a/tool/speed.cc b/tool/speed.cc
index 5d724e7..8aa8f85 100644
--- a/tool/speed.cc
+++ b/tool/speed.cc
@@ -1343,6 +1343,7 @@
       !SpeedHash(EVP_sha1(), "SHA-1", selected) ||
       !SpeedHash(EVP_sha256(), "SHA-256", selected) ||
       !SpeedHash(EVP_sha512(), "SHA-512", selected) ||
+      !SpeedHash(EVP_blake2b256(), "BLAKE2b-256", selected) ||
       !SpeedRandom(selected) ||
       !SpeedECDH(selected) ||
       !SpeedECDSA(selected) ||