[LyX/master] Implement reference-to-paragraph in outliner (#1624)

[Jürgen Spitzmüller]

Am Montag, dem 29.07.2024 um 08:50 +0200 schrieb Jürgen Spitzmüller:
> Strange, I cannot reproduce.

Meanwhile I could. Should be fixed, along with some other glitches
related to multi-buffer documents.

There is still a problem with inserting a ref to a caption in a sibling
document; I will address this separately as it might include more
extensive changes.

-- 
Jürgen