some c++11 support

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9426 a83610d8-ad2a-0410-a6ab-fc0612d85776
some defensive programming. cleanup unused boost include. tighten up boost includes

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@9427 a83610d8-ad2a-0410-a6ab-fc0612d85776