In v24 you called JS_InitClass and passed in a definition of JSNative
functions. Later you could call JS_NewObject with this class and the
object would get a prototype with the specified JSNative functions.
In ESR31 you now have to explicitly store the prototype object returned
by JS_InitClass and pass it as prototype argument to JS_NewObject to
achieve the same.
This change modifies our existing ScriptInterface implementation for
custom object types a bit and uses it at places where the JSAPI was used
directly before.
Refs #2462
This was SVN commit r15524.