Changeset 300f6a48 in rtems for cpukit/posix/src

score: Rework thread priority management

Add priority nodes which contribute to the overall thread priority.

The actual priority of a thread is now an aggregation of priority nodes.
The thread priority aggregation for the home scheduler instance of a
thread consists of at least one priority node, which is normally the
real priority of the thread. The locking protocols (e.g. priority
ceiling and priority inheritance), rate-monotonic period objects and the
POSIX sporadic server add, change and remove priority nodes.

A thread changes its priority now immediately, e.g. priority changes are
not deferred until the thread releases its last resource.

Replace the _Thread_Change_priority() function with

• _Thread_Priority_perform_actions(),
• _Thread_Priority_add(),
• _Thread_Priority_remove(),
• _Thread_Priority_change(), and
• _Thread_Priority_update().

Update #2412.
Update #2556.