Here's counter.idl:

#include <Bonobo.idl>

interface Counter: Bonobo::Unknown {
  readonly attribute short value;
  void incr();
  void decr();
  string name();
};

And here's the output after compilation: 

dpm@microstar:~/swdev/bonobo/revcounter$ orbit-idl-2 counter.idl
orbit-idl-2 2.14.3 compiling
  mode, hide preprocessor errors, passes: stubs skels common headers 

Processing file counter.idl
Error: `Bonobo' undeclared identifier

** (orbit-idl-2:24946): WARNING **: counter.idl compilation failed