Exports:  C name access
    Exporting C names to embedded Python code as object attributes
        - Embedding to run Python code from C
        - Extending to allow Python code to access C names

Regist:  callback handlers
    Exporting C functions to register callable Python objects, to be
    called in embedded mode from C on events
        - Embedding to run call Python objects passed in from Python code
        - Extending to export functions for registration and event triggers