Brush jumps to pointer

This button allows you to choose between two different 
relationships between the cursor (or pointer) and the brush
during brushing.

When you press the left or middle button during brushing,
either the brush jumps to the pointer or the pointer
jumps to the brush.  Experience shows that users have 
exceedingly strong preferences about these behaviors, so
both have been made available.

This can be set in the XGobi resource file.  The default is

*jumpBrush:   True

