Fix shadowed iterator variable in GaussLegendreXW

[ejanzer]

The for loop in GaussLegendreXW initializes an iterator variable it that shadows a previously declared it outside the loop. The outer it is compared to MAXIT, but because it's shadowed it's never updated, so the panic will never be triggered if it did not converge.

A linter surfaced this issue for me. I don't know how to test it, though...

[cpmech]

Hi, thanks for the fix. Testing this case it's tricky because we need to find a failing problem. But don't worry, I'll work on this in the upcoming weeks. Thanks again.