MSC: size_t _msize( void *block )

	MSC: size_t _bmsize( _segment seg, void _based( void ) *block )
	MSC: size_t _fmsize( void far *block )
	MSC: size_t _nmsize( void near *block )


	- prototype in malloc.h

	- returns size of memory block in bytes
	- _msize() maps to other function depending on memory model