[aarch64-port-dev ] RFR: aarch64: Add Arrays.fill stub code

[Long Chen]

Hi

Please review this patch for generating stub code for ArrayFill on aarch64
platform.

Performance test case:
http://people.linaro.org/~long.chen/ArrayFill/ArrayFill.java
Testing result: http://people.linaro.org/~long.chen/ArrayFill/ArrayFill.html
Patch: http://people.linaro.org/~long.chen/ArrayFill/ArrayFill.patch

At same time, refactoring ClearArrayNode's code generation, as it can be
used by Array fill too.

Following up I would like to propose a patch to use DC ZVA for large array
zeroing.

Jtreg tested and no regression.

Regards!