These examples show how typemaps can be used to remap various
SWIG datatypes.

argv          - How to pass Tcl lists as char **
constants     - Remap integer constants with a hash table.
return        - Return function arguments
interp        - Pass the Tcl_Interp * value into a C function

These examples only work with Tcl 7.x at this time.   The same
principles can be applied to Tcl 8.x, but this will require 
more time to learn all of the details of the new Tcl object
interface.