Add lengthSqr

[any1here]

No description provided.

[tonis2]

@any1here Isn't the sq_magnitude function already doing same thing ?

https://github.com/c3lang/c3c/blob/master/lib/std/math/vector.c3#L6-L7

[lerno]

Yes there are those functions that already exist. So maybe we could close this? For future PRs, note that methods also use snake case style, so that the method would have to be length_sqr.

[any1here]

Yes there are those functions that already exist. So maybe we could close this? For future PRs, note that methods also use snake case style, so that the method would have to be length_sqr.

Is there a reason why the length method is in math.c3 and sq_magnitude in vector.c3?
Also, the naming is confusing since one uses length while the other uses magnitude.