Merge branch 'pdf' into docs-next

Akira says:

This series resolves issues listed below:

 1. Some of chapter and section counts in Table of Contents (TOC) in
    large PDF docs collide with chapter/section titles, e.g., Chapters 10,
    11, 12, and 13 and Section 10.10 in userspace-api.pdf.
 2. In docs of more than 99 pages, page counts in TOC are not aligned
    properly when maxdepth >= 2 is specified in toctree, e.g., Chapters 10,
    12, and 13 in userspace-api.pdf
 3. In TOC of Latin-script docs, quotation and apostrophe symbols look too
    wide, e.g., Section 2.2 in userspace-api.pdf.
 4. In TOC of translations, Korean chapter titles lose inter-phrase spaces.
 5. On systems without "Noto Sans CJK" fonts, CJK chapters in translations
    results in full of "TOFU" boxes, with a long build time and a large
    log file containing lots of missing-font warnings.
 6. In translations.pdf built by "make pdfdocs", ascii-art diagrams in CJK
    are not aligned properly.