[NTG-context] \mathopen, \Uover and friends

Hi Hans, Thanks for the quick fix of today's upload. I could typeset your examples with \mathopen, \mathclose and these are great features in order to fine tune the spacing in math mode. Regarding the new command \Uover, I thought maybe it would be more consistent to have the usual structure ${1} \Uover {2}$ like the more friendly ${1} \over {2}$ instead of having $\Uover{1}{2}$ which is more like the \frac structure. Also a structure like $\Uover style \textstyle{1}{2}$ seems a little bit far from the usual ConTeXt atmposphere… Would it not be possible to have ${1} \Uover[style=textstyle] {2}$ instead? In any case, thanks a lot for the constant addition of cute features… Best regards: Otared K.