[jdk8u-dev] RFR: 8285802: AArch64: Consistently handle offsets in MacroAssembler as 64-bit quantities

[Andrew Haley]

This is a backport of [8285802](https://github.com/openjdk/jdk/commit/df4d5cf5f53c1451487e6301d31c196fac029f7a) from the openjdk/jdk repository. It's almost clean, but upstream mainline has a few
cleanups of integer type handling, so there is some additional backporting risk.

-------------

Commit messages:
 - 8285802: AArch64: Consistently handle offsets in MacroAssembler as 64-bit quantities

Changes: https://git.openjdk.java.net/jdk8u-dev/pull/50/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk8u-dev&pr=50&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8285802
  Stats: 13 lines in 3 files changed: 0 ins; 0 del; 13 mod
  Patch: https://git.openjdk.java.net/jdk8u-dev/pull/50.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk8u-dev pull/50/head:pull/50

PR: https://git.openjdk.java.net/jdk8u-dev/pull/50