RFR: 8370314: Update signals_posix with new Linux signal codes [v2]

[David Holmes]

> There are a few "new" si_codes defined on Linux that we did not support for error reporting. Some of these are only exposed in more recent glibc versions so we have to hard-wire them for older build environments.
> 
> The changes are all conditional on Linux, except the POLL_IN addition which is conditional on SIGPOLL, which is turn only exists on Linux.
> 
> Tested with local Linux environments, plus our CI plus GHA.
> 
> Thanks.

David Holmes has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into 8370314-posix-signals
 -  8370314: Update signals_posix with new Linux signal codes

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29105/files
  - new: https://git.openjdk.org/jdk/pull/29105/files/0be67ad8..e4d76bae

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29105&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29105&range=00-01

  Stats: 17923 lines in 562 files changed: 3878 ins; 2403 del; 11642 mod
  Patch: https://git.openjdk.org/jdk/pull/29105.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29105/head:pull/29105

PR: https://git.openjdk.org/jdk/pull/29105