This and the following commits will import NIST's ECC test vectors.
Right now all our tests pass if I make P-224 act like P-521, which is
kind of embarrassing. (Other curves are actually tested, but only
because runner.go tests them against BoGo.)

Change-Id: Id0b20451ebd5f10f1d09765a810ad140bea28fa0
Reviewed-on: https://boringssl-review.googlesource.com/10700
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>