[code-reflection] RFR: Avoid boxing when concatenating a string with a primitive

[Mourad Abbay]

Avoid boxing when concatenating a string with a primitive.

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Commit messages:
 - Avoid boxing when concatenating a string with a primitive

Changes: https://git.openjdk.org/babylon/pull/226/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=226&range=00
  Stats: 68 lines in 2 files changed: 67 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/babylon/pull/226.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/226/head:pull/226

PR: https://git.openjdk.org/babylon/pull/226