Array addition and array sum Panama benchmarks

[Roland Westrelin]

Looking at the unrolled variants:

>  .scalarArrayArray             4741341.171 ops/s
>  .unrolledArrayArray           1236491.068 ops/s
>  .scalarUnsafeArray           10972240.434 ops/s
>  .unrolledUnsafeArray          5700087.751 ops/s

scalarArrayArray and scalarUnsafeArray should perform the same as their
unrolled counterpart but don't. I filed
https://bugs.openjdk.org/browse/JDK-8328678 for that. The issue seems to
be that heuristics that drive unrolling (and vectorization which depends
on unrolling) are too conservative when the loop is hand unrolled.

Roland.