Fix issue 0002962 'Call-time pass-by-reference'

Thanks to kilroysoft for the rough recipe for fixing it. I'm not 100% happy with the solution but it's the only easy one and at least it gets rid of the errors.

• csv_export.php: pass all the values for the filter function by reference

• view_all_bug_page.php: pass all the values for the filter function by
  reference

• core/filter_api.php
  (filter_get_bug_rows): indicate all parameters are to be passed by reference
  and therefor, sadly, cannot be optional any more

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@1971 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9