Fix crash reported in bug #926

This fixes an icky memory leak in the guile code.
Minor tweak to previous commit.

The goal is to avoid certain kinds of very rare multi-threaed races.
Merge branch 'master' of github.com:opencog/opencog into swagger
Merge pull request #928 from ceefour/swagger

Make REST API documentation easier to use using Swagger
Merge remote-tracking branch 'opencog/master' into swagger
Additional documentation from the Wiki.

@cosmoharrigan Refs #927, #928.