<issue_start><issue_comment>Title: Update math.c for the new style
username_0: Part of the #720 effort
<issue_comment>username_0: I did update some of the docs as I went, making "Returns" used consistently, switching to "the natural logarithm of x", as well as adding small macro for when math constants were defined.
<issue_comment>username_1: Looks good. I think we can remove all reference  to the JDOC macro now though, which I will delete after we finish this porting process. The bootstrapping special handling has been moved into the JANET_CORE_* macros.
<issue_comment>username_0: So, my C-macro-fu isn't up to the task right now. I'll try to come back to this in a couple days if someone else doesn't get something written up for it, but I want to make sure that we have a macro for defining constants, rather than just defining a macro in math.c that might not follow the bootstrapping process.
<issue_comment>username_1: Thanks, the JANET_DEF macros look good as well.
<issue_comment>username_0: Fixed the merge conflicts with the ev.c changes