RFR: TCL sample fails because generated code is too large.

[Athijegannathan Sundararajan]

But we only use 3 functions. Using filtering fixes the same jextraction step.

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Commit messages:
 - TCL sample fails because generated code is too large. But we only use

Changes: https://git.openjdk.org/jextract/pull/116/files
 Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=116&range=00
  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jextract/pull/116.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/116/head:pull/116

PR: https://git.openjdk.org/jextract/pull/116