INT 62 u - FGDRIVER v4.02 - "FG_VBUNDEF" - RELEASE HANDLE FOR VIRTUAL BUFFER
	AX = 00D9h
	BX = virtual buffer handle
Notes:	the FGDRIVER functions are rearranged with each major release, but
	  their parameters do not change (see #03474)
	the specified handle must not reference the currently-active virtual
	  buffer
SeeAlso: AX=00D1h,AX=00D5h