Procedure RemoveLeading (StIn:String; Var StOut:String;
                             Const RemoveSet:CharSet);

    This  removes  characters  from   the   beginning  of  StIn  until  a
    character not in RemoveSet is reached.

    Example

    If StIn = 'Hi There Hi' and RemoveSet = [' ','J','Z','H',i']
    then the result, StOut = 'There Hi'.

    As 'H', 'i' and ' '  are  in  RemoveSet  they  are  removed  from the
    front of StIn.