LSM hooks: CPU scheduler

[vadorovsky]

First of all, decide if and how we want to define policies in regards to the following LSM hooks relate to task scheduling:

 * @task_setnice:
 *	Check permission before setting the nice value of @p to @nice.
 *	@p contains the task_struct of process.
 *	@nice contains the new nice value.
 *	Return 0 if permission is granted.
 * @task_setioprio:
 *	Check permission before setting the ioprio value of @p to @ioprio.
 *	@p contains the task_struct of process.
 *	@ioprio contains the new ioprio value
 *	Return 0 if permission is granted.
 * @task_getioprio:
 *	Check permission before getting the ioprio value of @p.
 *	@p contains the task_struct of process.
 *	Return 0 if permission is granted.
 * @task_prlimit:
 *	Check permission before getting and/or setting the resource limits of
 *	another task.
 *	@cred points to the cred structure for the current task.
 *	@tcred points to the cred structure for the target task.
 *	@flags contains the LSM_PRLIMIT_* flag bits indicating whether the
 *	resource limits are being read, modified, or both.
 *	Return 0 if permission is granted.
 * @task_setrlimit:
 *	Check permission before setting the resource limits of process @p
 *	for @resource to @new_rlim.  The old resource limit values can
 *	be examined by dereferencing (p->signal->rlim + resource).
 *	@p points to the task_struct for the target task's group leader.
 *	@resource contains the resource whose limit is being set.
 *	@new_rlim contains the new limits for @resource.
 *	Return 0 if permission is granted.
 * @task_setscheduler:
 *	Check permission before setting scheduling policy and/or parameters of
 *	process @p.
 *	@p contains the task_struct for process.
 *	Return 0 if permission is granted.
 * @task_getscheduler:
 *	Check permission before obtaining scheduling information for process
 *	@p.
 *	@p contains the task_struct for process.
 *	Return 0 if permission is granted.