Reapply r12489: Add pure, const and malloc attributes to proper functions

in libavutil.
Fix a compilation failure in r12489.

Originally committed as revision 12498 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/des.c

@@ -19,6 +19,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 #include <inttypes.h>
+#include "common.h"
 #include "des.h"
 
 #define T(a, b, c, d, e, f, g, h) 64-a,64-b,64-c,64-d,64-e,64-f,64-g,64-h