Fix 0002989: Allow managers to manage bugnotes.

M bugnote_view_inc.php

• Allowed users who have 'manage_project_threshold' to manage the notes
  by being able to Edit, Delete, Make Private or Make Public. Before only
  admins + reporter of the bugnote were able to do such behaviour.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@1999 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9