RFR: vcs: allow capital letters in e-mails

[Erik Helin]

Hi all,

please review this patch that allows e-mail addresses for the "Co-authored-by" lines to have capital letters for the
name part.

Testing:
- [x] Added a unit test
- [x] `make test` passes on Linux x64

Thanks,
Erik

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Commit messages:
 - vcs: allow capital letters in e-mails

Changes: https://git.openjdk.java.net/skara/pull/852/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=852&range=00
  Stats: 19 lines in 2 files changed: 18 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/852.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/852/head:pull/852

PR: https://git.openjdk.java.net/skara/pull/852