[jdk20] RFR: 8298225: [AIX] Disable PPC64LE continuations on AIX [v2]

[Tyler Steele]

> This small change adds an import to ppc.ad to allow it to find Contiuations::enabled, and sets VMContinuations to false on AIX.
> 
> Thanks to @TheRealMDoerr for suggestions to a previous version of this PR.

Tyler Steele has updated the pull request incrementally with one additional commit since the last revision:

  Removes indenting before #include macro in ppc.ad

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

Changes:
  - all: https://git.openjdk.org/jdk20/pull/4/files
  - new: https://git.openjdk.org/jdk20/pull/4/files/74c36006..d3c9a764

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk20&pr=4&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk20&pr=4&range=00-01

  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk20/pull/4.diff
  Fetch: git fetch https://git.openjdk.org/jdk20 pull/4/head:pull/4

PR: https://git.openjdk.org/jdk20/pull/4