[boost] [math] calculate derivative automatically.

Hi Bruno,

But I can help you if you want of course.I think the first step for you would be to learn about Boost.Proto as it's really the tool needed for that. Learn how to search/replace patterns in an expression. Thank your for your guidance, I am really appreciate your help. I am now going to learn about Boost.Proto. If I have some problem, we can talk about it.

Dongfei.