INT 21,46 - Force Duplicate File Handle

	AH = 46h
	BX = existing file handle
	CX = second file handle

	on return:
	AX = error code if CF set  (see DOS ERROR CODES)

	- if file handle in CX is currently open, current file
	  identified by CX is closed and the handle in BX is
	  dupped and placed in CX
	- after duping file handles move together through file
	- similar to INT 21,45