[vector] Intrinsics for fromByteArray, fromByteBuffer, intoByteArray, intoByteBuffer

[John Rose]

On May 3, 2018, at 8:40 AM, Paul Sandoz <paul.sandoz at oracle.com> wrote:
> 
> stick to native endianness for the moment to keep things simpler initially

I suggest throwing an exception if the buffer is in the wrong endianness.
We have regretted silently converting to native on other occasions.
— John