Fix printf warnings at -DDEBUG.

I must have not recompiled with debug printouts enabled since updating
the internal printf functions to have the gcc printf attribute, or
these warnings would surely have come up before.

utils.c

@@ -858,7 +858,7 @@ void debug_memdump(const void *buf, int len, bool L)
                 dputs("   ");          /* 3 spaces */
                 foo[i] = ' ';
             } else {
-                debug_printf("%c%02.2x",
+                debug_printf("%c%2.2x",
                         &p[i] != (unsigned char *) buf
                         && i % 4 ? '.' : ' ', p[i]
                     );