net: Remove ifa_ref()/ifa_free(), which are atomic(9), from ip_output()

This is backport from freebsd:

   commit 2c50988dca8f1c498ada4b3c8c0c275a7c324622
   Author: glebius <glebius@FreeBSD.org>
   Date:   Tue Mar 4 19:49:41 2014 +0000

       Remove ifa_ref()/ifa_free(), which are atomic(9), from ip_output().

       The ifaddr is already referenced by the rtentry, and we are holding
       reference on the rtentry throughout the function execution.

       Sponsored by:       Netflix
       Sponsored by:       Nginx, Inc.

Signed-off-by: Asias He <asias@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
net: Do not leak ifa in ip_output

This is backport from freebsd:

   commit ab0c56942296d702f3fb3e9418d3cde78711097b
   Author: glebius <glebius@FreeBSD.org>
   Date:   Wed Jul 9 07:48:05 2014 +0000

       In several cases in ip_output() we obtain reference on ifa. Do not
       leak it.

Signed-off-by: Asias He <asias@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
loader: get offset of list and set hooks in page_range

Hardcoded values are not nice and make it easy break something as
I demonstrated in 9202b75. Fixes #407.

Signed-off-by: Paweł Dziepak <pdziepak@quarnos.org>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>