RFR: 8286669: Replace MethodHandle specialization with ASM in mainline [v2]

[Jorn Vernee]

> Hi,
> 
> This PR brings over commits from the panama-foreign repo. These commits mostly pertain to the switch to ASM and away from MethodHandle combinators for the binding recipe specialization. But, there is one more commit which adds freeing of downcall stubs, since those changes were mostly Java as well.
> 
> Thanks,
> Jorn

Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:

  Use unaligned layout constants when filling in reconstituted structs (was accidentally dropped change)

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8685/files
  - new: https://git.openjdk.java.net/jdk/pull/8685/files/6e038edf..80640bac

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8685&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8685&range=00-01

  Stats: 22 lines in 1 file changed: 12 ins; 0 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8685.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8685/head:pull/8685

PR: https://git.openjdk.java.net/jdk/pull/8685