RFR: 8245986: AArch64: Provide information when hitting a HaltNode

[Andrew Haley]

We need to provide a halt reason when hitting a C2 HaltNode on
AArch64, and we need to do so without grossly bloating the code.

http://cr.openjdk.java.net/~aph/8245986/

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
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