[foreign-jextract] RFR: 8245003: jextract does not generate accessor for MemorySegement typed values

[Athijegannathan Sundararajan]

addressof accessor added for MemorySegment typed values (structs, unions, arrays).

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Commit messages:
 - 8245003: jextract does not generate accessor for MemorySegement typed values

Changes: https://git.openjdk.java.net/panama-foreign/pull/165/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/165/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8245003
  Stats: 274 lines in 7 files changed: 235 ins; 17 del; 22 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/165.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/165/head:pull/165

PR: https://git.openjdk.java.net/panama-foreign/pull/165