RFR: Changes and cleanups after review comments

[Ron Pressler]

Changes and cleanups after review comments

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

Commit messages:
 - -
 - Fix build
 - Merge branch 'fibers' into review1
 - Cleanup
 - Add a JNI test
 - cleanup
 - Merge branch 'fibers' into review1
 - Merge branch 'fibers' into review1
 - Cleanup
 - Add fuzz test case
 - ... and 13 more: https://git.openjdk.java.net/loom/compare/04a7c64b...97d749e4

Changes: https://git.openjdk.java.net/loom/pull/171/files
 Webrev: https://webrevs.openjdk.java.net/?repo=loom&pr=171&range=00
  Stats: 347 lines in 24 files changed: 163 ins; 78 del; 106 mod
  Patch: https://git.openjdk.java.net/loom/pull/171.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/171/head:pull/171

PR: https://git.openjdk.java.net/loom/pull/171