changed torrent::set_metadata() to reduce code duplication in metadata extensions. Exposed torrent_handle::set_metadata() to the public interface

include/libtorrent/torrent.hpp

@@ -638,7 +638,7 @@ namespace libtorrent
 		// to the checker thread for initial checking
 		// of the storage.
 		// a return value of false indicates an error
-		bool set_metadata(lazy_entry const& metadata, std::string& error);
+		bool set_metadata(char const* metadata_buf, int metadata_size);
 
 		int sequence_number() const { return m_sequence_number; }
 

include/libtorrent/torrent_handle.hpp

@@ -341,6 +341,7 @@ namespace libtorrent
 #endif
 
 		bool has_metadata() const;
+		bool set_metadata(char const* metadata, int size) const;
 		const torrent_info& get_torrent_info() const;
 		bool is_valid() const;