On Fri, 13 May 2016, Hans Åberg wrote:

> There may not be so many symbols: the “large operators" in the Tex Book, 
> p. 435, though Unicode have more, and some others like √ U+221A for 
> \sqrt.

If you want, you can collect such mappings in a separate module.

> I could not make your code working - does it require a later LuaTex 
> version (than 0.80.0)?

Here is a complete working example (OT: The location of the limit is still 
ugly with xits fonts)

\setupbodyfont[xits,10pt]

\appendtoks
      \catcode`∫=\activecatcode
      \letcharcode `∫ \int
\to \everymathematics
\setupmathematics[integral=nolimits]

Nolimits $\int_0^∞ f ω$, and $∫_0^∞ f ω$

\startformula
     \int_0^∞ f ω,\quad ∫_0^∞ f ω
\stopformula