INT 2F U - Windows95 - WRITE TO BOOT LOG                                        
	AX = 4A17h
	CX = number of bytes to write
	DS:DX -> message to write (must include CR-LF if it is desired)
Return: AX = status
	    0000h successful
	    FFFFh boot log file not open
	    else  DOS error code
Note:	calls the code for INT 2F/AX=4A21h after writing to the file
SeeAlso: AX=4A17h,AX=4A18h,AX=4A21h