Int 62 Fn 00D9  u - Fgdriver V4.02 - "fg_vbundef" - Release Handle For Vi  [V]

   AX = 00D9h
   BX = virtual buffer handle

Notes: the FGDRIVER functions are rearranged with each major release, but
     their parameters do not change (see #3145)
   the specified handle must not reference the currently-active virtual
     buffer

See Also: AX=00D1h,AX=00D5h