In OpenSSL, they're used in the 32-bit x86 Blowfish, CAST, DES, and RC5
assembly bits. We don't have any of those.

Change-Id: I36f22ca873842a200323cd3f398d2446f7bbabca
Reviewed-on: https://boringssl-review.googlesource.com/10780
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>

Initial fork from f2d678e6e8 (1.0.2 beta).

(This change contains substantial changes from the original and
effectively starts a new history.)