RFR: Latest scope locals changes. [v3]

[Andrew Haley]

> In particular, support for Structured Concurrency, but also some JMH tests.

Andrew Haley has updated the pull request incrementally with one additional commit since the last revision:

  Cleanup

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

Changes:
  - all: https://git.openjdk.java.net/loom/pull/46/files
  - new: https://git.openjdk.java.net/loom/pull/46/files/6edc5c2a..ea90a694

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=loom&pr=46&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=loom&pr=46&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.java.net/loom/pull/46.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/46/head:pull/46

PR: https://git.openjdk.java.net/loom/pull/46