OPENSSL_SMALL will still cause the smaller base-point table to be used
and so won't be as fast at signing as the full version, but Ed25519 will
now work in those builds.
Without OPENSSL_SMALL:
Did 20000 Ed25519 key generation operations in 1008347us (19834.4 ops/sec)
Did 20000 Ed25519 signing operations in 1025594us (19500.9 ops/sec)
Did 6138 Ed25519 verify operations in 1001712us (6127.5 ops/sec)
Did 21000 Curve25519 base-point multiplication operations in 1019237us (20603.6 ops/sec)
Did 7095 Curve25519 arbitrary point multiplication operations in 1065986us (6655.8 ops/sec)
With (on the same machine):
Did 8415 Ed25519 key generation operations in 1020958us (8242.3 ops/sec)
Did 8952 Ed25519 signing operations in 1077635us (8307.1 ops/sec)
Did 6358 Ed25519 verify operations in 1047533us (6069.5 ops/sec)
Did 6620 Curve25519 base-point multiplication operations in 1008922us (6561.5 ops/sec)
Did 7183 Curve25519 arbitrary point multiplication operations in 1096285us (6552.1 ops/sec)
Change-Id: Ib443c0e2bdfd11e044087e66efd55b651a5667e7
Reviewed-on: https://boringssl-review.googlesource.com/6772
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>