INT 13,0 - Reset Disk System

	AH = 00
	DL = drive number (0=A:, 1=2nd floppy, 80h=drive 0, 81h=drive 1)


	on return:
	AH = disk operation status  (see INT 13,STATUS)
	CF = 0 if successful
	   = 1 if error


	- clears reset flag in controller and pulls heads to track 0
	- setting the controller reset flag causes the disk to recalibrate
	  on the next disk operation
	- if bit 7 is set, the diskette drive indicated by the lower 7 bits
	  will reset then the hard disk will follow; return code in AH is
	  for the drive requested