sparse files fixes. now sets the size of the files in case sparse files are supported

src/file.cpp

@@ -245,6 +245,17 @@ namespace libtorrent
 			return ret;
 		}
 
+		void set_size(size_type s)
+		{
+			size_type pos = tell();
+			seek(1, 0);
+			char dummy = 0;
+			read(&dummy, 1);
+			seek(1, 0);
+			write(&dummy, 1);
+			seek(pos, 1);
+		}
+
 		size_type seek(size_type offset, int m)
 		{
 			assert(m_open_mode);
@@ -318,6 +329,11 @@ namespace libtorrent
 		return m_impl->read(buf, num_bytes);
 	}
 
+	void file::set_size(size_type s)
+	{
+		m_impl->set_size(s);
+	}
+
 	size_type file::seek(size_type pos, file::seek_mode m)
 	{
 		return m_impl->seek(pos, m.m_val);