*: use void * for printing pointers

On higher warning levels, compilers expect %p printf arguments to be
void *.  Since format string / argument warnings can be useful
otherwise, let's get rid of this noise by sprinkling casts to void *
over printf calls.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/bgpd/bgp_aspath.c b/bgpd/bgp_aspath.c
index cfa9bc1..191a9e7 100644
--- a/bgpd/bgp_aspath.c
+++ b/bgpd/bgp_aspath.c
@@ -1913,7 +1913,7 @@
 
   as = (struct aspath *) backet->data;
 
-  vty_out (vty, "[%p:%u] (%ld) ", backet, backet->key, as->refcnt);
+  vty_out (vty, "[%p:%u] (%ld) ", (void *)backet, backet->key, as->refcnt);
   vty_out (vty, "%s%s", as->str, VTY_NEWLINE);
 }