In [rand.req.eng] and [rand.req.dist], operator<< and operator>> are specified with fmtflags, which looks like an exposition-only data member but doesn't actually exist in the synopses. Presumably, we should use `flags()` instead and specify the function calls that change flags. Additionally, Postconditions should perhaps say "restored" instead of "unchanged".

Moreover, [rand.req.eng] p7 says "space character". But its meaning is unclear when `charT` is not a character type but a valid character container type, assuming the implementation allows instantiating `basic_ostream` with such a type.