[skara] RFR: 636: Quote @-characters in bridged emails

[Robin Westberg]

It's not enough to use \ to escape the @ character, so we can use this: @nomention instead to prevent unwanted mentions.

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Commit messages:
 - Add additional quoting of @ character

Changes: https://git.openjdk.java.net/skara/pull/1045/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1045&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-636
  Stats: 12 lines in 2 files changed: 10 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/skara/pull/1045.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1045/head:pull/1045

PR: https://git.openjdk.java.net/skara/pull/1045