INT 16 U - PCIBM PC Tools v5.1-8.0 DESKTOP - DISPLAY ASCIZA NUL-terminated ASCII string.	The ASCIZ string "ABC" consists of the four bytes 41h, 42h, 43h, and 00h.  Unless otherwise specified, maximum lengths given in the interrupt list do not include the terminating NUL. STRING CENTERED IN WINDOW
	AX = FFCCh
	DS:SI -> ASCIZA NUL-terminated ASCII string.	The ASCIZ string "ABC" consists of the four bytes 41h, 42h, 43h, and 00h.  Unless otherwise specified, maximum lengths given in the interrupt list do not include the terminating NUL. string
Return: AX = ???
	CX = ???
	ES:DI -> address past last character displayed (v5.1/5.5)
	      -> ??? on menu bar (v6.0)