Using int was a mistake. This patch changes String, StringImpl,
StringView and StringBuilder to use size_t instead of int for lengths.
Obviously a lot of code needs to change as a result of this.
Add a list of hard-coded standard types (including AK types) and show
them in a different style.
Rehighligt the file whenever it changes. (This is very inefficient but
makes it much easier to experiment.)
Also keep tweaking the colors. :^)
