vppinfra: add abstract socket & netns fns

* Add clib_socket_init support for abstract sockets
if name starts with an '@'
* Add clib_socket_init_netns to open socket in netns
* Add clib_netns_open

Type: feature

Change-Id: I89637ad657c702ec38ddecb5c03a1673d0dfb104
Signed-off-by: Nathan Skrzypczak <nathan.skrzypczak@gmail.com>
diff --git a/src/vppinfra/socket.h b/src/vppinfra/socket.h
index 78a56fe..fa5ef1e 100644
--- a/src/vppinfra/socket.h
+++ b/src/vppinfra/socket.h
@@ -93,6 +93,8 @@
    from IPPORT_USERRESERVED (5000). */
 clib_error_t *clib_socket_init (clib_socket_t * socket);
 
+clib_error_t *clib_socket_init_netns (clib_socket_t *socket, u8 *namespace);
+
 clib_error_t *clib_socket_accept (clib_socket_t * server,
 				  clib_socket_t * client);