CMakeList.txt fix

git-svn-id: http://svn.code.sf.net/p/libtorrent/code/trunk@10400 a83610d8-ad2a-0410-a6ab-fc0612d85776
fix some of the build errors in examples

git-svn-id: http://svn.code.sf.net/p/libtorrent/code/trunk@10405 a83610d8-ad2a-0410-a6ab-fc0612d85776