Make IntRange explicitly inclusive to [min, max].

[schmich]

It's not entirely clear, but it looks like IntRange was meant to be fully inclusive to the range [min, max]. Before this change, it was exclusive to max, i.e. the range was [min, max).

This change makes IntRange fully inclusive. This also fixes a bug in StringRange that was only generating strings up to max - 1 length (instead of generating strings up to max length as per its comment).

With this fix, the max == min case is handled automatically, so no switch is required. I also had to adjust the other utility functions to take into account the inclusive max.

If IntRange was meant to be [min, max) only, feel free to reject this PR, but I'd then recommend fixing StringRange and making it clear that IntRange excludes max.