Fossil SCM

Added "overflow-y: hidden;" to the CSS for the default skin to prevent some browsers (Chrome, Firefox, and Safari on macOS, at least) from adding a vertical scroll bar to the navbar. This was only necesasry on this skin because of the recently-added "overflow-x: auto" style, which tells the browser to clip or horizontally-scroll the navbar if the screen width isn't sufficient to show the whole thing; previously in this skin, and currently in all other skins, this condition causes the navbar to wrap to the next line, which looks particularly bad on the default skin. I believe this then made these browsers calculate some extra space for a possible horizontal scroll bar, which then ran the layout engine out of space, so it included the vertical bar just in case. This may be macOS specific, due to the scroll bar hiding behavior introduced several OS release back.