Add missing stdlib.h #include, fixes the warnings:

tools/trasher.c:44: warning: implicit declaration of function ‘atoi’
tools/trasher.c:53: warning: implicit declaration of function ‘abs’

Originally committed as revision 22328 to svn://svn.ffmpeg.org/ffmpeg/trunk

tools/trasher.c

@@ -19,6 +19,7 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <inttypes.h>
 
 static uint32_t state;