INT 21 - Attachmate Extra! - SEND KEYSTROKES TO HOST WINDOW                     
	AH = A3h
	AL = window number (1-4=host B-E)
	CX = 0001h
	DS:BX -> keystroke buffer
	DL = zero if keystroke buffer contains host function code (see #01799),
	      non-zero if keystroke buffer contains ASCII character
Return: CX = zero if character sent, non-zero if not
	BX incremented if CX=0


(Table 01799)
Values for Attachmate Extra! host function code:
 00h=reserved	10h=PF16	20h=Clear	30h=SysReq
 01h=PF1	11h=PF17	21h=Print	31h=ErInp
 02h=PF2	12h=PF18	22h=Left	32h=ErEof
 03h=PF3	13h=PF19	23h=Right	33h=Ident
 04h=PF4	14h=PF20	24h=Up		34h=Test
 05h=PF5	15h=PF21	25h=Down	35h=Reset
 06h=PF6	16h=PF22	26h=Home	36h=DevCncl
 07h=PF7	17h=PF23	27h=Fast Left	37h=Dup
 08h=PF8	18h=PF24	28h=Fast Right	38h=FldMark
 09h=PF9	19h=Alt on	29h=Bksp	39h=Enter
 0Ah=PF10	1Ah=Alt off	2Ah=Insert	3Ah=CrSel
 0Bh=PF11	1Bh=Shift on	2Bh=Delete
 0Ch=PF12	1Ch=Shift off	2Ch=Backtab
 0Dh=PF13	1Dh=PA1		2Dh=Tab
 0Eh=PF14	1Eh=PA2		2Eh=Newline
 0Fh=PF15	1Fh=PA3		2Fh=Attn