Int 21 Fn 64  U - OS/2 V2.0+ Virtual DOS Machine - Set Session Title       [O]

   AH = 64h
   DX = 0001h (function number)
   CX = 636Ch (magic value, "cl")
   BX = 0000h (indicates special request)
   ES:DI -> new ASCIZ title (max 12 char) or "" to restore default title

Note:  if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
     in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch

See Also: AH=64h/BX=0000h,AH=64h/BX=0002h,INT 15/AH=12h/BH=05h