RFR(L) Valhalla support for AArch64

[Roland Westrelin]

Hi Dmitry,

> http://cr.openjdk.java.net/~dsamersoff/valhalla_lworld_aarch64/webrev.03

Your change to ClearArray in aarch64.ad is not correct. ClearArray now
takes an extra argument, the value to store in memory which is not
always zero. Your implementation doesn't use it.

> 2. Support for MatchVVEPNode is not implemented.
>
>       This work is in progress. Is there any specific tests?

It's a calling convention change so it goes with
ValueTypePassFieldsAsArgs.

Roland.