Added code to the "l10n.language" template to fall

Added code to the "l10n.language" template to fall
back to the two-letter lang code if a longer lang
does not have a <lang>.xml localization file.
And it falls back to the default lang if it can't
find that either.

Also fixed a bug for finding the lang attribute.
It was using the last() function, but in an
ancestor-or-self node set you want the first ancestor
(closest) with a lang value.

49c49
<                                |ancestor-or-self::*/@xml:lang)[last()]"/>
---
>                                |ancestor-or-self::*/@xml:lang)[1]"/>