Add a CPU affinity set to the TCB if SMP is enable and use this CPU set as a mask for determining which CPUs the thread may run on. Add an affinity field to the attrributes to permit controlling which CPUs a pthread may run on.  Implements pthread_att_setaffinity_np() and pthread_attr_getaffinity_np().

Rename cpuset_t to cpu_set_t which is the type used in some non-standard Linux/GNU interfaces.  Move definitions of cpu_set_t to include/sys/types.h.  Add prototypes for sched_setaffinity(), sched_getaffinity(), pthread_attr_setaffinity_np(), pthread_attr_getaffinity_np(), pthread_setaffinity_np(), and pthread_getaffinity_np().  No implementation is yet in place.

2. Move list of signal actions from the task TCB to the task group.  Signal handlers are a property of the entire task group and not of individual threads in the group.  I know, I preferred it the other way too but this is more compliant with POSIX.

Performance improvement:  Idle loop should not take MM semaphore if there is not garbage to be collected.  This can cause loss of performance and thrashing in tasking

SMP: Fix some non-SMP errors that crept in; fix a recursion problem; re-partition some functionality to improve design and readability