Extract and test the deterministic part of Miller-Rabin.

This way we test not only that we match expectations for primes and
composites but that the core test correctly reports false witnesses. I
made an initial attempt to gather some interesting test input, but
probably one can do better.

Change-Id: I7c29afb534bd6980ef42a893e86d86bd44af8349
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/38164
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>

sources.cmake

diff --git a/sources.cmake b/sources.cmake
index 8dc65e6..db14456 100644
--- a/sources.cmake
+++ b/sources.cmake
@@ -47,6 +47,7 @@
   crypto/evp/scrypt_tests.txt
   crypto/fipsmodule/aes/aes_tests.txt
   crypto/fipsmodule/bn/bn_tests.txt
+  crypto/fipsmodule/bn/miller_rabin_tests.txt
   crypto/fipsmodule/ec/ec_scalar_base_mult_tests.txt
   crypto/fipsmodule/ec/p256-x86_64_tests.txt
   crypto/fipsmodule/ecdsa/ecdsa_sign_tests.txt