procps: add support for linux namespaces

Each process in Linux has a /proc/<pid>/ns directory which contains
symbolic links to pipes that identify which namespaces that process
belongs to. This patch adds support for ps to display that information
optionally.

Signed-off-by: Aristeu Rozanski <arozansk@redhat.com>

proc/libprocps.sym

@@ -11,6 +11,8 @@ global:
 	escaped_copy;
 	free_slabinfo;
 	freeproc;
+	get_ns_id;
+	get_ns_name;
 	get_pid_digits;
 	get_slabinfo;
 	getbtime;