* score/include/rtems/score/heap.h, score/inline/rtems/score/heap.inl,
score/src/heapallocate.c, score/src/heap.c, score/src/heapextend.c,
score/src/heapresizeblock.c, score/src/heapwalk.c: Documenation.
Simplified block resize. Improved heap walk. Changed heap layout to
avoid a special case for _Heap_Is_used() and _Heap_Is_free().
* libmisc/stackchk/check.c: Update for heap API changes.