RFR: 8240914: java_lang_Throwable::fill_in_stack_trace should use Handler for "cont"

[Leonid Mesnik]

Also, includes fix for
JDK-8240924 Several more places where naked oop to cont should be handled

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Commit messages:
 - 8240924: Several more places where naked oop to cont should be handled
 - Merge branch 'fibers' into fillStackTraceCrash
 - name fixed.
 - Fix (workaround) for crach in java_lang_Throwable::fill_in_stack_trace

Changes: https://git.openjdk.java.net/loom/pull/9/files
 Webrev: https://webrevs.openjdk.java.net/loom/9/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8240914
  Stats: 13 lines in 1 file changed: 5 ins; 0 del; 8 mod
  Patch: https://git.openjdk.java.net/loom/pull/9.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/9/head:pull/9

PR: https://git.openjdk.java.net/loom/pull/9