cubicweb-localperms #1942604 xrexpr/xorexpr have inconsistent prototypes [resolved]

we should have a single, more generic, function

prioritynormal
typeenhancement
done in0.1.0
load0.100
load left0.000
closed by#b28a154247ae generic version of xrexpr to replace (inconsistent) xorexpr function (closes #1942604)