RFR: git: support unicode filenames [v2]

[Erik Helin]

> Hi all,
> 
> please review this patch that adds support for unicode filenames to `GitRepository`. I also added a unit test
> exercising the new functionality.
> Testing:
> - [x] `make test` passes on Linux x64
> - Added a new unit test
> 
> Thanks,
> Erik

Erik Helin has refreshed the contents of this pull request, and previous commits have been removed. The incremental
views will show differences compared to the previous content of the PR. The pull request contains one new commit since
the last revision:

  git: support unicode filenames

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

Changes:
  - all: https://git.openjdk.java.net/skara/pull/728/files
  - new: https://git.openjdk.java.net/skara/pull/728/files/11c70886..3097f5b7

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=skara&pr=728&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=skara&pr=728&range=00-01

  Stats: 16 lines in 2 files changed: 1 ins; 13 del; 2 mod
  Patch: https://git.openjdk.java.net/skara/pull/728.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/728/head:pull/728

PR: https://git.openjdk.java.net/skara/pull/728