Summary for users: Previously, Code Context displayed a fixed number of lines.  Often, many were blank.  Hence the default *numlines* to display was small, 3, to avoid having too many blank lines.  However, 3 is often too small to display the complete context.

Now, Code Context initially displays a single blank line for 'no context', to show that the feature is active.  When the top visible line is part of an indented body, the context used as many non-blank lines as needed, up to a maximum of *maxlines*, which has a default of 15.  Because a new configuration option is used, there should be no interference between user settings for old releases and future releases. 

Initially, context lines are added to an expanded editor window.  When the height of the window has been maximized, perhaps with the zoomheight feature, and when the height of the window has been reset with the mouse, context lines replace normal code text.