[O] Embedded LaTeX fontification

[Kai von Fintel]

When I embed LaTeX code in a `#+BEGIN_SRC latex` block and 
`org-src-fontify-natively` is set to `t`, the code is fontified as LaTeX 
code. But when the code is embedded in a `#+BEGIN_LaTeX` block, there's 
no fontification. Is that as intended? Am I missing some setting? Or 
could that functionality be added?

-- Kai.