Auto-fix for certain error messages

Some error messages suggest a fix. For example, "Not in scope" is often accompanied by "Perhaps you meant: " When one of these errors is encountered, one idea is to add a button to the output window that labeled "Fix it" that will automatically make the change.

This does raise the question of what to do if the original source has been edited. The easy answer would be to disable or remove these buttons. But that actually sounds like an annoying experience. A better answer would be to track markers in the source code that follow the location as edits are made, and only disable the button if an edit happened in that region of the code.