Mnu class structure:
~~~~~~~~~~~~~~~~~~~~~
create class Mnu from Win
  export:
  var Help       //{}
  var Items      //{}
  var SelItems   //{}
  var Cursor     //(object of Cursor)
  var Choice     //1
  var Top        //1
  var CanAppend  //false
  var InsBlock   //{|o|nil}
  var DelBlock   //{|o|nil}
  method New=MnuNew         //o:New() --> self
  method Init=MnuInit       //o:Init(Name,R,C,CurSize,Items,SelItems,Clr,Shd) --> true
  method Process=MnuProcess //o:Process() --> nChoice
  method Done=MnuDone       //o:Done() --> true
  endclass