RFR: 8303002: Reject packed structs from linker [v2]

[Jorn Vernee]

> This patch adds checks in AbstractLinker to reject packed structs and structs with excess padding (e.g. unnamed bitfields), since both of those are currently not supported, and the ABI/spec seems too vague to base support on.

Jorn Vernee has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13164/files
  - new: https://git.openjdk.org/jdk/pull/13164/files/e11fc6b5..e11fc6b5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13164&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13164&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13164.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13164/head:pull/13164

PR: https://git.openjdk.org/jdk/pull/13164