Call VioWrtTTY with:
	STACK:	WORD	VIO handle (must be 00h)
		WORD	length of string
		DWORD	pointer to character string to be written to screen
Return: AX = error code (00h, 74h, 1B4h) (see #00373)
Notes:	write wraps at end of line and terminates if it reaches end of screen
	in ANSI mode, ANSI control sequences are interpreted, and this func is
	  not required to be reentrant; in non-ANSI mode, the function is
	  reentrant and may be called from within an MS-DOS function call