[debug] Use %p to print pointers

Fixes https://github.com/harfbuzz/harfbuzz/issues/640

src/hb-debug.hh

@@ -93,7 +93,7 @@ _hb_debug_msg_va (const char *what,
   fprintf (stderr, "%-10s", what ? what : "");
 
   if (obj)
-    fprintf (stderr, "(%0*lx) ", (unsigned int) (2 * sizeof (void *)), (unsigned long) obj);
+    fprintf (stderr, "(%*p) ", (unsigned int) (2 * sizeof (void *)), obj);
   else
     fprintf (stderr, " %*s  ", (unsigned int) (2 * sizeof (void *)), "");