remove unused variables. add some comments

git-svn-id: svn://svn.code.sf.net/p/libtorrent/code/trunk@10494 a83610d8-ad2a-0410-a6ab-fc0612d85776
merged changes from RC_1_0

git-svn-id: svn://svn.code.sf.net/p/libtorrent/code/trunk@10495 a83610d8-ad2a-0410-a6ab-fc0612d85776