Update for Xcode 4.6: remove unneded cast

git-svn-id: http://gtm-http-fetcher.googlecode.com/svn/trunk@112 b3aa69f0-f65c-a609-0a27-78855af037c1
Fetcher changes for better thread safety

git-svn-id: http://gtm-http-fetcher.googlecode.com/svn/trunk@113 b3aa69f0-f65c-a609-0a27-78855af037c1