RFR: 2373: Support repo-<project> style fix versions

[Erik Joelsson]

This patch adds parsing logic for handling version strings on the form "repo-<project>". This form is commonly used in JBS for project repos, but Skara is currently unable to actually parse them.

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Commit messages:
 - SKARA-2373

Changes: https://git.openjdk.org/skara/pull/1686/files
  Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1686&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2373
  Stats: 31 lines in 3 files changed: 31 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/skara/pull/1686.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1686/head:pull/1686

PR: https://git.openjdk.org/skara/pull/1686