RFR(S): 8231055: C2: arraycopy with same non escaping src and dest but different positions causes wrong execution

[Roland Westrelin]

Thanks for the review, Tobias.

> Small suggestions:
> - The comment in macro.cpp:388 is a bit misleading. I would use something like: "Non constant offset
> in the array: We can't statically determine the value"
> - You don't need a new @bug line in the test but can just add the new bug number separated by a
> whitespace.

I went with your suggestions.

http://cr.openjdk.java.net/~roland/8231055/webrev.01/

Roland.