RFR: 8274136: -XX:+ExitOnOutOfMemoryError calls exit while threads are running

[David Holmes]

Please see bug report for more detailed discussion.

We introduce `os::_exit()` to `call _exit()` to allow us to terminate without running the at_exit handlers and global destructors, which lead to the crashes during termination.

Testing: tiers 1-3 (includes the ExitOnOutOfMemoryError test)

Thanks,
David

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

Commit messages:
 - 8274136: -XX:+ExitOnOutOfMemoryError calls exit while threads are running

Changes: https://git.openjdk.java.net/jdk/pull/5668/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5668&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274136
  Stats: 16 lines in 4 files changed: 12 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5668.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5668/head:pull/5668

PR: https://git.openjdk.java.net/jdk/pull/5668