document that @math should contain only TeX/LaTeX and use httex?

[Patrice Dumas]

Hello,

Given that Michal from tex4ht said that httexi should be difficult to
fix such that the output is true html and not a rendition as text, what
about
* using httex to convert @math content with tex4ht too in the default
  case
* document in the manual that if one want to use
  tex4ht/latex2html/Mathjax, that is any of the HTML_MATH possibilities
  the best is to used only TeX/LaTeX math in @math{}, no @-command, and 
  even better, math common with LaTeX and eTeX.

-- 
Pat