MINOR add hook for extensions to update current page id, before falling back to default

code/controllers/CMSMain.php

@@ -811,6 +811,8 @@ class CMSMain extends LeftAndMain implements CurrentPageIdentifier, PermissionPr
 	public function currentPageID() {
 		$id = parent::currentPageID();
 		
+		$this->extend('updateCurrentPageID', $id);
+
 		// Fall back to homepage record
 		if(!$id) {
 			$homepageSegment = RootURLController::get_homepage_link();