This isn't all of our pointer games by far, but for any code which
doesn't run on armv6, memcpy and pointer cast compile to the same code.
For code with does care about armv6 (do we care?), it'll need a bit more
work. armv6 makes memcpy into a function call.

Ironically, the one platform where C needs its alignment rules is the
one platform that makes it hard to honor C's alignment rules.

Change-Id: Ib9775aa4d9df9381995df8698bd11eb260aac58c
Reviewed-on: https://boringssl-review.googlesource.com/17707
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>