RFR: pr: configure fork names explicitly

[Erik Helin]

Hi all,

please review this small patch that allows fork names to be configured a bit more freely for the PR bot.

Thanks,
Erik

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Commit messages:
 - pr: configure fork names explicitly

Changes: https://git.openjdk.java.net/skara/pull/1015/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1015&range=00
  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/skara/pull/1015.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1015/head:pull/1015

PR: https://git.openjdk.java.net/skara/pull/1015