MSC: int _heapset( unsigned fill )

		MSC: int _bheapset( _segment seg, unsigned fill )
		MSC: int _fheapset( unsigned fill )
		MSC: int _nheapset( unsigned fill )


	- prototype in malloc.h

	- heapset maps to the other functions depending on memory model
	- first check heap consistency via heapchk() then fills memory
	  with value specified in "fill"

	- returns one of the following:

	  _HEAPOK	heap is ok
	  _HEAPBADBEGIN initials allocation header couldn't be found
	  _HEAPBADNODE	heap/node has been damaged
	  _HEAPEMPTY	heap has not been initialized

	- see	heapchk()   heapwalk()