RFR: 760: Wrong "On ..., XXX wrote:" in comment on PR

[Robin Westberg]

The mailing list bridge bot could fail to match quoted text and `@mentions`. This improves the matching.

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Commit messages:
 - Improve parent detection

Changes: https://git.openjdk.java.net/skara/pull/919/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=919&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-760
  Stats: 94 lines in 2 files changed: 85 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/skara/pull/919.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/919/head:pull/919

PR: https://git.openjdk.java.net/skara/pull/919