docs: add missing ids, avoid duplicates

This commits combines the effect of the following commits
from KDE/4.9:

26195cffd560f046a5ea0b98a7edecb56f38ca9a
17fc976ca4eb29f56b8c61667d714b287cec97a2 (*)
730cd2f83c7847f030464ae003e3eded8fb1cb02
bcb962e2460376623d710c8be3d116dc11a2ed45 (*)
09388c4e5cb97fb33604c4c273aa359863082ba5

where (*) marks partial or total reverts; cherry-picking each single
commit would have introduced more noise in this branch