[cppia] Cyptic error message when cppia bytecode does not match host

[kevinresol]

On mac, I got the following error message when the cppia bytecode does not match the host binary. This is mostly due to invalid/mismatched extern definitions to the host classes. It would be nice if the message is clearer, perhaps at least mention "cppia", so it is easier to debug.

libc++abi: terminating due to uncaught exception of type Dynamic