cryptography.io depends on this. Specifically, it assumes that any time
a CBC-mode cipher is defined, CMAC is also defined. This is incorrect;
CMAC also requires an irreducible polynomial to represent GF(2^b).
However, one is indeed defined for 64-bit block ciphers such as 3DES.

Import tests from CAVP to test it. I've omitted the 65536-byte inputs
because they're huge and FileTest doesn't like lines that long.

Change-Id: I35b1e4975f61c757c70616f9b372b91746fc7e4a
Reviewed-on: https://boringssl-review.googlesource.com/28466
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>