Overful hbox for \part in ToC

[kopeckyf]

In ToC, \part produces an overful hbox.
It is presently unclear whether this was intended by the authors of scrbook.
This bug was reported by the editor of Marianne Mithun's Mohawk grammar.

[stefan11]

I guess it is because of the bold numbers. They are a bit larger.

[kopeckyf]

Figure 15.3 from scrguide exemplifies a dilemma:

• not increasing pagenumberwidth will lead to many page number in the ToC to be not aligned with the right margin of the type area
• increasing pagenumberwidth will lead to less space for the titles of parts, chapters, subsections, etc.

Idea: increase pagenumberwidht only for \part entries in the ToC.