Things to do in Rexx/Tk
- add itemconfigure to mclistbox for Tcl/Tk 8.3 and above
- make czTclCommand a variable length. It is currenty a fixed length
  and that restricts the length of a Rexx/Tk command to about 2000 bytes.
- Finish OS/2 port, once Illya Vaes finishes the OS/2 port of Tcl/Tk
