another attempt at fixing broadcast_socket.cpp, windows build

git-svn-id: svn://svn.code.sf.net/p/libtorrent/code@10531 a83610d8-ad2a-0410-a6ab-fc0612d85776
mingw fix in CMakeLists.txt

git-svn-id: svn://svn.code.sf.net/p/libtorrent/code@10532 a83610d8-ad2a-0410-a6ab-fc0612d85776
fix typo

git-svn-id: svn://svn.code.sf.net/p/libtorrent/code@10533 a83610d8-ad2a-0410-a6ab-fc0612d85776