fix typo

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9709 a83610d8-ad2a-0410-a6ab-fc0612d85776
merged mingw fix from RC_0_16

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9711 a83610d8-ad2a-0410-a6ab-fc0612d85776