A DESCRIPTION OF THE PROBLEM :
The proposed patch is an improvement for Byte/Short/Int/LongBuffer classes to add compareToUnsigned() that works like compareTo() but treats the values as unsigned to leverage the vectorized mismatch implementations, which are not publicly accessible.

In addition to that, it adds mismatch() for all *Buffer classes.

Both new methods basically expose all the goodness of jdk.internal.util.ArraysSupport to *Buffer.

The patch includes adoptions to the existing unit tests as well.

Paul Sandoz: "The addition of mismatch is reasonable. I am unsure about compareToUnsigned, since we are trying to be a conservative about what we add to Buffer."

(webbug as requested by Paul Sandoz on core-libs-dev ML)