Gradient check method is not compatible with the latest PCL

[jiancong0204]

Hi Koide,

thank you so much for your great work! However, I just found that the gradient test method you use for gicp's optimization progress is not compatible with that of the official PCL since this commit 3854 They just provided a virtual function, which has to be overridden when implementing, for checking the gradient when using bfgs algorithm.

the corresponding code in your project is here

By writing this issue, I am just wondering if you had plan to modify this project to be compatible with the latest PCL.

Looking forward to your reply and best regards,
Jiancong