(filter_db_get_available_queries): Changed api to take project id and user id as parameters. The parameters are default to null. If null, they are set to current project / current user.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@3001 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9