Bug #43950 myisamchk shows negative value for 'Max keyfile length'

While printing the Max keyfile length 'llstr' call was used which 
was treating the max_key_file_length as negative.

Changing this to ullstr fixes the problem. 
myisamchk output will differ in 32 bit and 64 bit Operating systems 
so its not possible to have test case for this bug.

myisam/myisamchk.c

@@ -1311,7 +1311,7 @@ static void descript(MI_CHECK *param, register MI_INFO *info, my_string name)
 	  share->base.max_key_file_length != HA_OFFSET_ERROR)
 	printf("Max datafile length: %13s  Max keyfile length: %13s\n",
 	       llstr(share->base.max_data_file_length-1,llbuff),
-	       llstr(share->base.max_key_file_length-1,llbuff2));
+               ullstr(share->base.max_key_file_length - 1, llbuff2));
     }
   }