+ changes in dynamic memory allocation
 - there are 3 separated dyanamic allocators
   1. kMem : Kernel heap allocator (which is protected from accessing by user thread)
   2. shMem : Shared heap allocator whose section has no limit to access (any thread / kernel can access without limit)
   3. uMem : user heap allocator whose section can only be access from child thread of same parent thread(root)
+ some significant changes are derived by this structural fix
   1. Only one heap allocator for root thread (per process)
   2. heap allocator is shared among children of root thread
   3. stack of children is allocated from this user heap allocator
this change will improve following
  1. stability in multi process operation (memory protection can be easily adopted)
  2. security (another process can not access another process memory)