[jdk11u-dev] RFR: 8286562: GCC 12 reports some compiler warnings

[Zdenek Zambersky]

Backport fixes few warnings in newer gcc (12+), which I have seen some when doing test build for gcc15 (fedora 34) for another [backport](https://github.com/openjdk/jdk11u-dev/pull/3087#issuecomment-3266882552). Warning do not show in current GHA runs because it uses gcc 10. (Btw this change has also been backported to oracle jdk 11.)

Backport is not clear, there were some differences in surrounding context, copyright headers, location of gmk file etc. So part of it had to be done manually.  Changes to jfrTraceIdBits.inline.hpp are not present, because modified function is not present on jdk11.

I also included backport of followup change ([JDK-8293691](https://bugs.openjdk.org/browse/JDK-8293691)), which fixes problem introduced by original backported change.

GHA tests: OK

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Commit messages:
 - Backport f2a32d996ae09620474771c46a649f6c4e1148ad
 - Backport 410a25d59a11b6a627bbb0a2c405c2c2be19f464

Changes: https://git.openjdk.org/jdk11u-dev/pull/3091/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=3091&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286562
  Stats: 41 lines in 5 files changed: 27 ins; 1 del; 13 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/3091.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/3091/head:pull/3091

PR: https://git.openjdk.org/jdk11u-dev/pull/3091