[foreign-abi] RFR: 8238316: jextract emits a C_BOOL when source says char

[Athijegannathan Sundararajan]

foreign-abi change to create instance for each MemoryLayout instance.

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Commits:
 - 0f64ade3: use separate instance for primitive layouts

Changes: https://git.openjdk.java.net/panama-foreign/pull/22/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/22/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8238316
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/22.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/22/head:pull/22

PR: https://git.openjdk.java.net/panama-foreign/pull/22