Add Archive.supported_formats (array of strings)

Helpful for scripts that want to know what file types (extensions) are
supported by the Archive class object.

Still need to work out the JSDOC support for this. Similar to the
Socket class object properties, this will have no documentation/description.

src/sbbs3/js_archive.c

@@ -705,11 +705,21 @@ JSClass js_archive_class = {
 
 JSObject* js_CreateArchiveClass(JSContext* cx, JSObject* parent)
 {
-	return JS_InitClass(cx, parent, NULL
+	JSObject* obj = JS_InitClass(cx, parent, NULL
 		,&js_archive_class
 		,js_archive_constructor
 		,1		/* number of constructor args */
 		,NULL	/* props, set in constructor */
 		,NULL	/* funcs, set in constructor */
 		,NULL, NULL);
+	if(obj != NULL) {
+		jsval val;
+		if(JS_GetProperty(cx, parent, js_archive_class.name, &val) && !JSVAL_NULL_OR_VOID(val)) {
+			JSObject* constructor;
+			JS_ValueToObject(cx, val, &constructor);
+			js_CreateArrayOfStrings(cx, constructor, "supported_formats", supported_archive_formats
+				,JSPROP_PERMANENT|JSPROP_ENUMERATE|JSPROP_READONLY);
+		}
+	}
+	return obj;
 }