Renderer::line_no is a confusing name

[epage]

What is no, nomber?

Is line_num / line_number the best name? I feel like this is the gutter style but its also used for .... Unsure what to call that.

We should probably change this to something else. If we want, we can smooth out the upgrade path by offering the name in a current version, deprecating the old name, and then removing the old name in a new version.