added missing include of set.hpp
added missing include of set.hpp

mildred/rasterbar-libtorrent,mildred/rasterbar-libtorrent,mildred/rasterbar-libtorrent,mrmichalis/libtorrent-code,mrmichalis/libtorrent-code,mildred/rasterbar-libtorrent,mrmichalis/libtorrent-code,mrmichalis/libtorrent-code,mrmichalis/libtorrent-code,mildred/rasterbar-libtorrent,mrmichalis/libtorrent-code,mildred/rasterbar-libtorrent