Add hook into get_user_locale()

[juliobox]

Hey there

Like its friend get_locale(), get_user_locale() could benefit of a filter hook named "user_locale".

What do you think?

[vanaf1979]

My patch ads a 'user_locale' filter to the get_user_locale function.

I do have two question though:

• get_user_local can return the users locale or the sites local. Should the filter have a second "is_user_local" paramater?

• if there is no user locale the get_user_locale function returns the value of get_locale which already has a 'locale' filter. This makes the value be filtered twice. I'm not sure if this is desired?