[code-reflection] Integrated: Allow mandel example to run without UI

[Gary Frost]

Allow Mandel to run headless.  To allow PTX testing on machine without X11

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Commit messages:
 - Allow mandel example to run without UI

Changes: https://git.openjdk.org/babylon/pull/164/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=164&range=00
  Stats: 834 lines in 6 files changed: 777 ins; 13 del; 44 mod
  Patch: https://git.openjdk.org/babylon/pull/164.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/164/head:pull/164

PR: https://git.openjdk.org/babylon/pull/164