Added core_gpc_API.php which is the best name Jeroen and I can come up with to hold these functions. It makes the get functions short which was important. We could also move any cookie-manipulating functions into this file at some point.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@1322 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9