INT 21,C - Clear Keyboard Buffer and Invoke Keyboard Function

	AH = 0C
	AL = 01, 06, 07, 08 or 0A   (INT 21 input functions)


	on return:
	see return values from INT 21,AL where AL is 1, 6, 7, 8 or A


	- main function is to clear the input buffer and call INT 21h with
	  the specified function (in AL)
	- see INT 21,1,  INT 21,6,  INT 21,7,  INT 21,8 & INT 21,A