bug#43205: 28.0.50; Eldoc protocol not useful for third-party packages

[Yuan Fu]

Currently the documentation of `eldoc-documentation-functions' says this:

* `:thing', VALUE is a short string or symbol designating what is
being reported on.  The documentation display engine can elect
to remove this information depending on space contraints;

without saying what VALUE could be. For someone who want to write a
frontend to display eldoc signitures, this is useless. For someone who
want to write a documentation backend for eldoc, this is useless as
well. I think the protocol should at least specify what VALUE could be
expected: signature? full-doc? example? links?



Also contraints is spelled wrong. And on line 705.