[foreign-abi] RFR: 8248421: CSupport should have a way to free memory allocated outside Java

[Athijegannathan Sundararajan]

Added CSupport.freeMemoryRestricted utility method.

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Commit messages:
 - missed source changes
 - 8248421: CSupport should have a way to free memory allocated outside Java

Changes: https://git.openjdk.java.net/panama-foreign/pull/281/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/281/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8248421
  Stats: 98 lines in 3 files changed: 98 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/281.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/281/head:pull/281

PR: https://git.openjdk.java.net/panama-foreign/pull/281