move ed25519.hpp into main libtorrent include directory, since it's part of the API now

git-svn-id: http://libtorrent.googlecode.com/svn@10125 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda
merged changes from RC_1_0

git-svn-id: http://libtorrent.googlecode.com/svn@10126 f43f7eb3-cfe1-5f9d-1b5f-e45aa6702bda