move more documentation into headers

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@8773 a83610d8-ad2a-0410-a6ab-fc0612d85776
moved more documentation over from manual to headers

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@8775 a83610d8-ad2a-0410-a6ab-fc0612d85776
merged encoding issue fix from RC_0_16

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@8778 a83610d8-ad2a-0410-a6ab-fc0612d85776