Data tables and dropdowns render right

Two rounds of base-layer fidelity for the everyday web, each checked pixel for pixel against the reference browser. Data tables got three real fixes at once. A table caption now sits directly above its table, or below it when asked, instead of being hoisted into the top corner of the page where every caption piled on top of the next. Every gridlined table drawn with collapsed borders now shows its full frame: the right edge of the last column and the bottom edge of the last row used to go unpainted, so a plain bordered table rendered open on two sides, and now the box is closed on all four. And a cell that spans several rows centres its content vertically the way the reference browser does, rather than pinning it to the top. On forms, a dropdown now shows its chevron: a closed select used to look identical to a plain text field, and now carries the small downward arrow that marks it as a menu, drawn in the control's own text colour so it reads on dark selects too.