Chat-80 port to Ciao

This is a port of Chat-80 to Ciao packaged as a Ciao bundle. It can be installed with:

$ ciao get github.com/ciao-lang/chat80

Then it can be started with:

$ chat80

Chat-80 was a prototype natural language question answering system developed by David H. D. Warren and Fernando Pereira in 1982. See the original paper for a more detailed description (recovered from the web archive).