RFR: 8280840: Update libFFI to 3.4.2

[Alexander Matveev]

LibFFI updated to 3.4.2. No additional changes to our code, libffi code or build system were required. Tested on all platforms.

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Commit messages:
 - 8280840: Update libFFI to 3.4.2 [v2]
 - 8280840: Update libFFI to 3.4.2

Changes: https://git.openjdk.java.net/jfx/pull/738/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=738&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280840
  Stats: 3463 lines in 34 files changed: 927 ins; 38 del; 2498 mod
  Patch: https://git.openjdk.java.net/jfx/pull/738.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/738/head:pull/738

PR: https://git.openjdk.java.net/jfx/pull/738