Mark funtions returning Result as #[must_use]

[Masterchef365]

Mark functions returning Result as #[must_use], so that if the 'out' variable is not mutated, the program is sure to do something about it.

I realized that this case might be important if rsparse is used for e.g. robotic control where the output of e.g. lusol, stored in b here: lusol(a: &Sprs, b: &mut [T], order: i8, tol: T) may not have been touched, and could contain an invalid or otherwise dangerous solution. Previously, this would have been avoided by panicking, but now using Result introduces this possibility.

[RLado]

I just learned something new. Thank you!