implement syntax highlighting as an array of color information, with per-line indexes

[bombasticbob]

implement syntax highlighting as an array of color information, with per-line indexes. Editing or inserting a line would have to make room for the color info, and temporarily lock out (and re-start) any background threads that are currently scanning the document.

color information would only be displayed when valid. Otherwise, use the default color. When "it becomes valid", the window will need to be invalidated. This should be made possible from a worker thread [currently there's no threading support for events].

[bombasticbob]

see #5