Initial support for cgroups

Similar to how systemd creates cgroups for all services, for purposes of
tracking, Finit now does the same.  We also mount all available cgroups
in the /sys/fs/cgroup namespace.

This patch adds support for grouping processes in logical cgroups, like
systemd, and an `initctl ps` command to list the hieararchy.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

src/getty.c

@@ -32,6 +32,7 @@
 #include <termios.h>
 
 #include "finit.h"
+#include "cgroup.h"
 #include "helpers.h"
 #include "sig.h"
 #include "utmp-api.h"
@@ -192,6 +193,7 @@ static int do_login(char *name)
 {
 	struct stat st;
 
+	cgroup_user(name);
 	execl(_PATH_LOGIN, _PATH_LOGIN, name, NULL);
 
 	/*