Fix issue 0003002 - "User 'administrator' is not able to change other users settings"

• account_prefs_update.php
  • check if $f_user_id is unprotected instead of the current user
  • if f_user_id is not the current user, perform an additional access check

NOTE: I'm not sure we should be sharing this file between the account section and
manage section. Having to add that conditional access check is a little ugly and
who knows if the pages will always be the same. Most of the code should be in an
API function anyway.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2026 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9