+* BREAKING CHANGE: Implementation of MediaWiki's JS and JSON value encoding
+ has changed:
+** MediaWiki no longer supports PHP installations in which the native JSON
+ extension is missing or disabled.
+** XmlJsCode objects can no longer be nested inside objects or arrays.
+ (For Xml::encodeJsCall(), this individually applies to each argument.)
+** The sets of characters escaped by default, along with the precise escape
+ sequences used, have changed (except for the Xml::escapeJsString()
+ function, which is now deprecated).
+* BREAKING CHANGE: The Services_JSON class has been removed. If necessary,
+ be sure to upgrade affected extensions at the same time (e.g. Collection).