All error object should now be cloned with fast_clone_object() or better.
Reinstated the freeing of err->error_message and err->error_backtrace now that the error objects are properly initialized.
Added some more Autodoc mk II about the compiler.

Rev: src/cpp.c:1.170
Rev: src/dynamic_load.c:1.92
Rev: src/error.c:1.162
Rev: src/object.c:1.293
Rev: src/program.c:1.707