math/scilab: upgrade to 2026.1.0 and undeprecate
Latest releases notes at
https://gitlab.com/scilab/scilab/-/blob/2026.1.0/scilab/CHANGES.md
Also take maintainership.
This is a first attempt at an upgrade of this port. It is usuable, but
not perfect: don't hesitate to send patches!
Known limitations:
- I've not been able to get a dynamic libary_path, this explains the
work-around in etc/jvm_options.xml, and a non-breaking exception when
starting;
- MAKE_JOBS_UNSAFE has to be set, should be avoidable with some fixes in
the makefiles;
- FreeBSD is not officially supported, and no Atoms modules are available
for us ATM.