[Modules] protected_envvars configuration option

[Xavier D. <xav...@gm...>]

Hello All,

protected_envvars is a new configuration option that will be part of next
version (5.2). With this option it is possible to list environment
variables that could not be modified by the modulefiles.

See
https://modules.readthedocs.io/en/latest/module.html#envvar-MODULES_PROTECTED_ENVVARS

Many thanks to Adrien Cotte for this contribution.

Regards,
Xavier