&$alldata: The localisation data from core and extensions
&purgeBlobs: whether to purge/update the message blobs via MessageBlobStore::clear()
+'LocalisationCacheRecacheFallback': Called for each language when merging
+fallback data into the cache.
+$cache: The LocalisationCache object
+$code: language code
+&$alldata: The localisation data from core and extensions. Note some keys may
+ be omitted if they won't be merged into the final result.
+
'LocalisationChecksBlacklist': When fetching the blacklist of
localisation checks.
&$blacklist: array of checks to blacklist. See the bottom of