Available from version 1.19.0 (r94435, codereview)
allows to set prefix for a spefific link table
Define function:
public static function onBacklinkCacheGetPrefix( $table, &$prefix ) { ... }
Attach hook: In extension.json:
	"Hooks": {
		"BacklinkCacheGetPrefix": "MediaWiki\\Extension\\MyExtension\\Hooks::onBacklinkCacheGetPrefix"
Called from: File(s): cache/BacklinkCache.php
Interface: BacklinkCacheGetPrefixHook.php

For more information about attaching hooks, see Manual:Hooks .
For examples of extensions using this hook, see Category:BacklinkCacheGetPrefix extensions.