improve gzip error handling

git-svn-id: http://libtorrent.googlecode.com/svn@9805 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda
merged fix from RC_0_16

git-svn-id: http://libtorrent.googlecode.com/svn@9806 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda
fix build

git-svn-id: http://libtorrent.googlecode.com/svn@9807 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda
merged changes from trunk

git-svn-id: http://libtorrent.googlecode.com/svn@9808 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda