Merge branch '3.1.x'

* 3.1.x:
  [ticket/13950] Hide undefined categories
  [ticket/13950] Hide undefined permissions

phpBB/phpbb/permissions.php

@@ -159,6 +159,28 @@ class permissions
 		return (isset($this->permissions[$permission]['cat'])) ? $this->permissions[$permission]['cat'] : 'misc';
 	}
 
+	/**
+	* Checks if a category has been defined
+	*
+	* @param	string	$category	Identifier of the category
+	* @return	bool	True if the category is defined, false otherwise
+	*/
+	public function category_defined($category)
+	{
+		return isset($this->categories[$category]);
+	}
+
+	/**
+	* Checks if a permission has been defined
+	*
+	* @param	string	$permission	Identifier of the permission
+	* @return	bool	True if the permission is defined, false otherwise
+	*/
+	public function permission_defined($permission)
+	{
+		return isset($this->permissions[$permission]);
+	}
+
 	/**
 	* Returns the language string of a permission
 	*