Fix 0003080: project menu bar shows extra links

• core/html_api.php
  (print_project_menu_bar): add a DISTINCT clause to the query that pulls out
  the list of projects (we should be able to use the project_api functions
  for this.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2126 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9