bug#48518: 13.0.11; LaTeX environment C-c C-e on region doesn't indent properly

[Berthold Lorke]

It seems that it still doesn't work quite right for any environments 
listed in `LaTeX-indent-environment-list`, for example `equation`, 
`align`, `cases`, `picture`, among many others.

Furthermore, I noticed the following.

If after selecting the environment, there is no additional prompt, say 
for example for `cases`, the opening and closing `\begin{cases}` and 
`\end{cases}` get indented correctly, but the content enclosed in it 
(which was previously the highlighted region) stays unchanged.

If after selecting the environment, there is an additional prompt, say 
for example for `equation`, the opening `\begin{equation}` gets indented 
correctly, but the closing `\end{equation}` has no indentation at all 
(id est is all the way left starting at column 0), and the content 
enclosed also behaves as described before, unchanged indentation.

It should be easy to reproduce, I don't even think it is necessary to 
already be in an indented environment to see this behaviour, but one can 
try inside of an `itemize` environment for example, with wrongly 
indented text spanning multiple lines and the highlight starting in the 
middle of a line to see the effect the best.