Merged requested to merge mnauw/json-glib:valid-double-exponential into master
As mentioned in the referenced issue #67 (closed) a double may be serialized incorrectly. For example,
1e-08 is serialized as
1e-08.0 (which is not a valid double, at least not according to JSON spec; https://www.json.org/json-en.html). This patch follows the suggestion in the issue and also adds a minor test.