RFR: vthreads don't support the reserved stack zone [v2]

[Dean Long]

> vthreads don't support the reserved stack zone

Dean Long has updated the pull request incrementally with one additional commit since the last revision:

  redo

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

Changes:
  - all: https://git.openjdk.java.net/loom/pull/120/files
  - new: https://git.openjdk.java.net/loom/pull/120/files/df139bc5..06f83010

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=loom&pr=120&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=loom&pr=120&range=00-01

  Stats: 13 lines in 3 files changed: 1 ins; 11 del; 1 mod
  Patch: https://git.openjdk.java.net/loom/pull/120.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/120/head:pull/120

PR: https://git.openjdk.java.net/loom/pull/120