slirp: Fix type casts and format strings in debug code

Casting pointers to long won't work on 64 bit Windows.
It is not needed with the right format strings.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Jason Wang <jasowang@redhat.com>
diff --git a/slirp/ip_output.c b/slirp/ip_output.c
index c82830f..1254d0d 100644
--- a/slirp/ip_output.c
+++ b/slirp/ip_output.c
@@ -60,8 +60,8 @@
 	int len, off, error = 0;
 
 	DEBUG_CALL("ip_output");
-	DEBUG_ARG("so = %lx", (long)so);
-	DEBUG_ARG("m0 = %lx", (long)m0);
+	DEBUG_ARG("so = %p", so);
+	DEBUG_ARG("m0 = %p", m0);
 
 	ip = mtod(m, struct ip *);
 	/*