[Maxima] Imaxima and imath home page adds inline graph tutorial

[John Lapeyre]

> The direct link to the tutorial web page is:
> http://members3.jcom.home.ne.jp/imaxima/Site/Tutorial_of_Imaxima_(inline_gr
>aph).html
>

imaxima is a great environment. The tutorial above says:

  Please refer to the Maxima manual entries of these commands
  to know how to use wx-prefixed versions of these commands

But in maxima 5.15.0, wxplot2d appears in neither the online,
nor html manual.