Refactor search input and watchlist buttons CSS

Make the search input and watchlist buttons exactly the same height.
Fix the styling of the non-JS Go button.

Also, remove .divclearable (it changes HTML in cached pages, but the new
CSS works both with old and new HTML).

Change-Id: I69234c93064d1ae34b1d1b41734db7a0fdf2d4ad
Merge "Refactor search input and watchlist buttons CSS"