Changed the options and how they interact because I wanted to see what it would be like.
* scrollwheel_lines (4): Number of lines for normal scrolling. Still don't know how to get the system default.
* scrollwheel_alt_factor (6): Multiplier when alt is pressed, instead of pgup/pgdown. This is like a scrolling accelerator. Users can set it to scroll less than a full page so that context from jump to jump is still visible.
* scrollwheel_ctrl_lines (4): Number of lines to scroll when control is pressed, when it doesn't activate zooming. Fine scrolling is easier if set to a low number, like 1.
* scrollwheel_ctrl_zoom (T): Whether ctrl+scroll = zoom.