The changes to the assembly files are synced from upstream's
64d92d7498. cpu-intel.c is translated to C
from that commit and d84df59440.

Change-Id: I02c8f83aa4780df301c21f011ef2d8d8300e2f2a
Reviewed-on: https://boringssl-review.googlesource.com/18411
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>