Introduces Textpattern_L10n_Locale.

Sets and gets locale. A wrapper for system setlocale.
It's a spin from the old, strangely named getlocale(),
with the difference that:

* It allows setting any category opposed to just LC_TIME.
* Updates the identifier table to more complete state.
* Packs in the extra methods used in safe_strtime().

E.g.

Txp::get('L10nLocale')->setLocale(LC_ALL, 'da-dk');

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5557 2fea6a4d-a838-0410-917b-93a53c48e9d2