[foreign-jextract] RFR: 8260717: jextract crashes with 'Crossing storage unit boundaries' for libcoap's block.h

[Athijegannathan Sundararajan]

bitfield handling overhaul

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Commit messages:
 - 8260717: jextract crashes with Crossing storage unit boundaries for libcoaps block.h

Changes: https://git.openjdk.java.net/panama-foreign/pull/445/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=445&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260717
  Stats: 228 lines in 8 files changed: 218 ins; 7 del; 3 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/445.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/445/head:pull/445

PR: https://git.openjdk.java.net/panama-foreign/pull/445