RFR: 8285792: Posix signal handler modification checking issues. [v3]

[Harold Seigel]

> Please review this fix for JDK-8285792.  The fix removes print statements from check_signal_handler() so that it doesn't print all the handlers every time it finds one that is modified.  Instead, it returns true if the handler is modified, false otherwise.  Its caller, user_handler(), then prints all the handlers just once even if multiple signal handlers were modified.
> 
> The fix also adds a check for VMError::crash_handler_adress() to check_signal_handler() to prevent it from being treated as a signal handler modification.
> 
> The fix was tested with Mach5 tiers 1-2 on Linux and Mac OS and Mach 5 tiers 3-5 on Linux x64.  The regression test is excluded on Windows.
> 
> Thanks, Harold

Harold Seigel has updated the pull request incrementally with one additional commit since the last revision:

  SIGFPE change

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9631/files
  - new: https://git.openjdk.org/jdk/pull/9631/files/f57603ff..45515f59

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9631&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9631&range=01-02

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/9631.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9631/head:pull/9631

PR: https://git.openjdk.org/jdk/pull/9631