RFR: vcs: add method Patch.toString

[Erik Helin]

Hi all,

please review this small patch that adds the method `Patch.toString`.

Thanks,
Erik

-------------

Commit messages:
 - vcs: add method Patch.toString

Changes: https://git.openjdk.java.net/skara/pull/878/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=878&range=00
  Stats: 15 lines in 1 file changed: 15 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/878.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/878/head:pull/878

PR: https://git.openjdk.java.net/skara/pull/878