t8code does not compile with `-Wextra` and/or `-Wpedantic`

[jmark]

Would be nice to fully to support these flags, too.

[lukasdreyer]

Those are the additional warnings that arise:

-Werror=unused-parameter, fixed by introducing [[maybe_unused]] https://en.cppreference.com/w/cpp/language/attributes/maybe_unused

-Werror=type-limits, fixed by removing the unnecessary unsigned int >= 0 assertion

-Werror=implicit-fallthrough=, fixed by not allowing switch statements to fall through

-Werror=ignored-qualifiers, fixed by removing const return qualifier

[holke]

#1158 fixes parts of the fallthroughs.

[holke]

#1118 is related

[dutkalex]

#1414 should solve this

[spenke91]

@sandro-elsweijer @lukasdreyer Do you agree that this issue is fixed and can be closed? I checked it locally and heard from others that it works for them too...

[sandro-elsweijer]

@spenke91 yes we can close this :)