Add a subtle drop shadow to the search results dropdown.
Restore the old site's default search, which is to try the quickref first.

This is actually an improvement on the old site, really, because the previous
case of "all php.net sites" is handled by the last item in the dropdown. My
inclination for now is to not worry about the other search modes that were
supported in the old site's search bar: many of them are for subsites that have
their own search, such as bugs.php.net and pecl.php.net, and the others have
tabs on results.php anyway.
Improve the styling on the search results page.

I hacked this together for the old version of the new site, and it really
didn't fit in with the new aesthetic. This is an attempt to improve it to stick
out less like a sore thumb and more like a slightly itchy one instead.