bug#74785: 27.1; Fill-paragraph in RST mode does not respect line blocks

[Stefan Monnier]

>>>    | This is the all the first line
>>>      of output even though it's two lines
>>>      of input.
>>>    | This is second line in the output.
>>>    | And this is the third.
[...]
>> Stefan and Stefan, any ideas or suggestions?

[ With all those Stefans around I feel like nothing can stop us.  ]

I think we "just" need to:

- set `paragraph-start` to match a line with a leading `|`.
- set `adaptive-fill-regexp` to match this leading `|`.

If the `paragraph-start` setting makes paragraph navigation inconvenient
(too fine-grained), we could try and set
`fill-forward-paragraph-function` to a function which let-binds
`paragraph-start` around a call to `forward-paragraph`.


        Stefan