#676 Fixed many small mouse-triggered-zoom bugs

[dima]

Before this patch

• zoom-around-mouse (ctrl-wheel) did not work with volatile data

• horizontal zoom (shift-ctrl-wheel) was not mouse-centered

• the bounds of inactive axes (those with VERYLARGE bounds) were being changed
  when zooming. Now the bounds stay at +-VERYLARGE regardless of zooming

The causes of these issues (fixed in this patch) were improper handling of the
log axes, not paying attention to the order of bounds (in case an axis was
reversed), etc

[dima]

This is a duplicate of 677. Sorry; sourceforge got confused.