INT 21,7 - Direct Console Input Without Echo

	AH = 07


	on return:
	AL = character from STDIN


	- waits for keyboard input until keystroke is ready
	- character is not echoed to STDOUT
	- returns 0 for extended keystroke, then function must be
	  called again to return scan code
	- ignores Ctrl-Break and Ctrl-PrtSc
	- see	INT 21,1