Tag Pack

The attached patches, which apply to the current SVN release, are a partial attempt to improve the multilanguage support of Tag Pack.
Maybe someone can find them useful, although a lot could be done to get a more complete solution.

The target is: on a multilanguage site, make the page editors able to define different tags for each page language. When using the Tag Pack FE plugin, only the tags connected to the contents written in the current language should be displayed.
The attached patches try to solve the FE part of the problem: they allow to display only the tags related to the contents available in the current language.

Jo Hasenau once suggested to me: "The problem with pages is, that they are using an overlay table to get translated records. You have to make the overlay table taggable as well, but this would not include the FE tagcloud out of the box, so I'm not quite sure this would be working."

I have tried to work around this by patching the code a little.
Basically I've added some conditions in order to handle cases where the "pages" table is requested and the language is not the default one. In those cases the information is taken from "pages_language_overlay" table instead of "pages".
I haven't changed anything about handling other tables.

The trick seems to work, at least in my little sandbox.
I am sure my code can be largely improved, though.