Language used in representations and preferences. A language tag is composed
of one or more parts: A primary language tag and a possibly empty series of
subtags. When formatted as a string, parts are separated by hyphens.
author: Jerome Louvel (contact@noelios.com)
Returns the language associated to a name. If an existing constant exists
then it is returned, otherwise a new instance is created.
Parameters: name - The name. The associated language.