RFR: jcheck: add symlink check

[Erik Helin]

Hi all,

please review this patch that adds a check for symbolic links to JCheck.

Testing:
- `make test` passes on Linux x64
- Added two new unit tests

Thanks,
Erik

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

Commit messages:
 - jcheck: add symlink check

Changes: https://git.openjdk.java.net/skara/pull/525/files
 Webrev: https://webrevs.openjdk.java.net/skara/525/webrev.00
  Stats: 252 lines in 9 files changed: 251 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/525.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/525/head:pull/525

PR: https://git.openjdk.java.net/skara/pull/525