Include stdlib.h for atoi declaration

Add $FreeBSD$ while I'm here.

usr.sbin/lpr/filters.ru/koi2alt/koi2alt.c

@@ -22,6 +22,8 @@
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
+ *
+ * $FreeBSD$
  */
 
 /*
@@ -31,6 +33,7 @@
 #include <sys/types.h>
 #include <signal.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <unistd.h>
 
 int length = 66;