RFR: 8378675: PPC64: increase instruction cache line size [v2]

[David Briemann]

> Set the instruction cache line size for Power to 128 bytes.
> 
> Add functions to retrieve the data cache line size and instruction cache line size from the system (AIX & Linux).

David Briemann has updated the pull request incrementally with two additional commits since the last revision:

 - add comments that explain getconf behavior
 - update copyright headers

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Changes:
  - all: https://git.openjdk.org/jdk/pull/29918/files
  - new: https://git.openjdk.org/jdk/pull/29918/files/516f9508..bb0973c1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29918&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29918&range=00-01

  Stats: 14 lines in 6 files changed: 4 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/29918.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29918/head:pull/29918

PR: https://git.openjdk.org/jdk/pull/29918