OpenSSL added a similar helper function. It's very, very common for us
to malloc something an then zero it. This saves some effort. Also
replace some more malloc + memcpy pairs with memdup.
Change-Id: I1e765c8774a0d15742827c39a1f16df9748ef247
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/63345
Reviewed-by: Bob Beck <bbe@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
Auto-Submit: David Benjamin <davidben@google.com>
David Benjamin