`\skelline` could be breakable

[mlhetland]

The \skelline command creates a single box of a certain width; if a wide \skelline is used in a paragraph, it will most likely protrude into the margin. While this use wasn't originally intended, it might very well be useful. A possible solution could be the following:

• Add a split key to \skelline.
• \skelline[split=n, x cm] would typeset n blocks, each of width x/n cm.
• The blocks are separated by \linebreak[0] to permit breaks.

Here n is the “resolution” (for line breaking). It could have some reasonable default (such as 10, perhaps). Beyond being breakable at the given points, the resulting skeleton element should look like the current \skelline.

The effect should be vaguely similar to, say, using lipsum along with censor (which could actually also be a straightforward way of achieving the effect).