Update jgit-describe.jar: "Update with support for .git-files rather than requiring .git to be a directory and Better support for windows"

Change-Id: I3e417aceb4dbecf9afd2968afd3525879643e795
Reviewed-on: http://gerrit.dmdirc.com/2341
Reviewed-by: Chris Smith <chris@dmdirc.com>
Automatic-Compile: DMDirc Build Manager