[foreign-memaccess] [Rev 02] RFR: Memory access implementation rewrite - post cleanup

[Maurizio Cimadamore]

> * Fix access modes not preserved in AbstractMemorySegmentImpl.ofBuffer
> * Add check to ensure that Foreign::withSize and Foreign::asMallocSegment are called with unchecked address

Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:

  Fixed recovery of correct thread ownership info when transitioning from segment -> buffer -> segment.
  Added test (contributed by Paul Sandoz)

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Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/111/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/111/files/a1bd77a2..9b56d7e4

Webrevs:
 - full: https://webrevs.openjdk.java.net/panama-foreign/111/webrev.02
 - incr: https://webrevs.openjdk.java.net/panama-foreign/111/webrev.01-02

  Stats: 46 lines in 2 files changed: 43 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/111.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/111/head:pull/111

PR: https://git.openjdk.java.net/panama-foreign/pull/111