Rearrange placement of #site-name strong

Originally in #253609: Add 'region' class to regions, JJeff says:

This patch also rearranges #site-name div to place the <strong> tag INSIDE the <a> instead of surrounding it. This makes it possible to make the 'a' tag into a block element, put a background image on it and then place the contents of the 'strong' tag off the page. The end result is basically an text replacement (usually a site logo) which is still clickable to return the user to the home page. Without the 'strong' tag inside the 'a' tag, this would be a much trickier maneuver.

And I replied:

I see the utility in this request. And while <strong><a>link</a></strong> seems more natural, the only other alternative HTML that would do what you want, <strong><a><span>link</span></a></strong>, is definitely no good.

I'm splitting this patch off from the rest of that discussion, so I can track them separately and apply this one first.