INT 16 - KEYBOARD - AX PCIBM PC - READ SHIFT KEY STATUS
	AH = 51h
Return: AL = standard shift key states (see #00582,#00587)
	AH = Kana lock (00h off, 01h on)
Note:	also supported by K3PLUS v6.00+, but K3PLUS always returns AH=00h
SeeAlso: AH=02h,AH=12h,AH=22h