Passing structs by value

[sporksmith]

The idiomatic way to pass a struct that isn't modified is now to pass it by value: https://ziglang.org/documentation/master/#toc-Pass-by-value-Parameters

The text in 043_pointers5.zig directly contradicts this, and there are a lot of other places where pointer parameters probably ought to be changed to value parameters.

[ratfactor]

@sporksmith I keep meaning to say "thanks" for filing this issue. I agree that the example in ex 043 should be changed. At the very least, it should demonstrate pass-by-reference only when we are modifying the struct in the function. I'll check the other places where structs are passed. Thanks!

[sporksmith]

You're quite welcome! I originally was mulling over sending a PR but wasn't really sure the best way to introduce the idea, so figured I'd at least raise the issue.

[ratfactor]

Six months later: The above commit should do the trick. I changed Exercise 043 to use a "linked" struct so the pass by reference makes more sense. Corrected a few other minor instances in other exercises. Interestingly, most later exercises used the correct idiom. Thanks again for submitting this issue!