Brew MP 1.0.2
This function lets go of (ungets) some or all of the last logical
line from the data source and replace the line terminators in the
Pointer to the IGetLine Interface object.
Specifies how much (up to the length of the last line) to let
go of (unget). This number must be less than or equal to nLen from the
GetLine structure filled by the last call to GetLine(), i.e. it must
NOT include the length of line terminator(s).