This example tests the %import directive and working with multiple modules.

Use 'lua runme.lua' to run a test.

Overview:
---------

The example defines 4 different extension modules--each wrapping
a separate C++ class.

     base.i     -  Base class
     foo.i      -  Foo class derived from Base
     bar.i      -  Bar class derived from Base
     spam.i     -  Spam class derived from Bar

Each module uses %import to refer to another module.  For
example, the 'foo.i' module uses '%import base.i' to get
definitions for its base class.
