[11u] RFR: JDK-8206895: aarch64: rework error-prone cmp instuction

[Lemmond, Dan]

Hello,

Please review this backport request for JDK-8206895<https://bugs.openjdk.java.net/browse/JDK-8206895>: aarch64: rework error-prone cmp instruction.

JBS: https://bugs.openjdk.java.net/browse/JDK-8206895
Webrev: http://cr.openjdk.java.net/~phh/8206895/webrev.11u.00/
Original review thread: https://mail.openjdk.java.net/pipermail/hotspot-dev/2018-July/033461.html

This backport required fixes to three hunks and the omission of one hunk entirely.

macroAssembler_aarch64.cpp required hunk 19 to be manually applied, and stubGenerator_aarch64.cpp required hunk 7 and 13 to be manually applied.

I have omitted hunk 15 from the backport as JDK-8218966<https://bugs.openjdk.java.net/browse/JDK-8218966> was backported previously, which overwrites that section with a bug fix.

The backport compiles without issue and passes all Tier1 Hotspot tests.

Thanks,
Dan