RFR: 8251438: Issues with our POSIX set_signal_handler() [v2]

[Gerard Ziemski]

> This is a fix for a potential issue involving "The storage occupied by sa_handler and sa_sigaction may overlap, and a conforming application shall not use both simultaneously." https://pubs.opengroup.org/onlinepubs/009695399/functions/sigaction.html, when we in fact do assume different storages.

Gerard Ziemski has updated the pull request incrementally with one additional commit since the last revision:

  change get_signal_handler to take pass by reference attribute

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1680/files
  - new: https://git.openjdk.java.net/jdk/pull/1680/files/123acb47..aedc4cd0

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1680&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1680&range=00-01

  Stats: 9 lines in 1 file changed: 0 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1680.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1680/head:pull/1680

PR: https://git.openjdk.java.net/jdk/pull/1680