Owner-draw source code so that we get a non-proportional font and can show
breakpoints and current position without using the selection mechanism.


Implement and remember breakpoints.  Must be very fast to determine whether
a line has a breakpoint
 
 - From ICI variables because we'll have to do it FOR EVERY LINE EXECUTED.
 - From line numbers for when we're owner-drawing the source code.


Remember window size, position and min/max/normal state.

