bug#36459: 27.0.50; octave-mode ElDoc support bug

[Mauro Aranda]

> Thank you for the patch. What is the recommended way to get function
> signatures these days if print_usage is deprecated?
>
> Leo

Hello Leo.

The deprecated function is usage, not print_usage.  The usage function
was deprecated in GNU Octave 4.0, and in the 4.4 version it
has been removed.

Here is the NEWS file that says usage is deprecated, and that its
replacement is print_usage:
https://www.gnu.org/software/octave/NEWS-4.0.html

Since it says print_usage is the replacement function, I think calling
print_usage is reliable.

Here is the NEWS file that says usage has been removed:
https://www.gnu.org/software/octave/NEWS-4.4.html

Best regards,
Mauro.