reorganize gpc_api a bunch
add gpcget*_array() functions
add gpc_get_cookie()
use gpc_get_cookie() in the auth_api
use gpc_get_int_array() in proj_user_add.php

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@1398 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9