rst: Evaluate per-task clone mask early

When we've read all pstree-items and their ids we
can get the desired clone-flags early and avoid all
these dances with flag calculations in fork_with_pid
and company.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/syscall-types.h

@@ -55,6 +55,8 @@ struct robust_list_head;
 #define CLONE_NEWNET	0x40000000
 #endif
 
+#define CLONE_ALLNS	(CLONE_NEWPID | CLONE_NEWNET | CLONE_NEWIPC | CLONE_NEWUTS | CLONE_NEWNS)
+
 #define setns	sys_setns
 
 struct rlimit;