Decoration calculation very slow since update to 4.3

[thederingSimus]

With the current version of subclipse (4.3.3), it takes Eclipse very long to update the status decorations of projects (triggered in my case by selecting working sets). VisualVM shows that java.nio.file.Files.isSymbolicLink() is using nearly all time in the thread doing the decoration calculation, so I guess that this problem comes from the fix for #84 that was introduced in 4.3.0.

Before the update, the status decorations were updated in ~2 seconds even for multiple projects, now it is taking ~10 seconds for one project and increases when more projects are being updated (~50 seconds for 8 projects). Here is a screenshot of VisualVM showing a sampler snapshot:

[markphip]

There are no longer any regular contributors to this project. If someone submits a PR that can fix this issue without breaking the other one I will do what I can to get it merged.

[movedoa]

Can we roll back #84? Now we have horrible performance for all decorators instead of a wrong decorator in one specific edge case.