Add GTM_NONNULL

git-svn-id: http://gtm-http-fetcher.googlecode.com/svn/trunk@114 b3aa69f0-f65c-a609-0a27-78855af037c1
Back out GTM_NONNULL declarations.

git-svn-id: http://gtm-http-fetcher.googlecode.com/svn/trunk@115 b3aa69f0-f65c-a609-0a27-78855af037c1
More GTM_NONNULL removal

git-svn-id: http://gtm-http-fetcher.googlecode.com/svn/trunk@116 b3aa69f0-f65c-a609-0a27-78855af037c1