critical: bug in stepsize for non-MKS models

[gnwong]

Christian Fromm identified a bug in the way the i-suite calculates stepsize: stepsize assumes X2 is bounded above by 1. See the relevant ipole line of code here:

https://github.com/AFD-Illinois/ipole/blob/63b2aa7b216bfe6ec16cbec46de0cce9ccf6986b/src/model_geodesics.c#L57

Perhaps the most correct way to deal with this is to include stepsize in the model files and (in the iharm model) explicitly load x2_max, since there's nothing in the iharm file format that forces x2_max == 1.

[bprather]

This is fixed in dev: https://github.com/AFD-Illinois/ipole/blob/dev/src/model_geodesics.c#L208

I fixed it specifically to implement bhac_mks coordinates

[gnwong]

The circle closes!