[foreign-jextract] RFR: 8249290: jextract does not handle void typedef in function pointer argument

[Athijegannathan Sundararajan]

void typedefs are handled to check the return type.

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Commit messages:
 - 8249290: jextract does not handle void typedef in function pointer argument

Changes: https://git.openjdk.java.net/panama-foreign/pull/243/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/243/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8249290
  Stats: 105 lines in 3 files changed: 102 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/243.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/243/head:pull/243

PR: https://git.openjdk.java.net/panama-foreign/pull/243