Sorting with unaryFun predicate

[Nordlöw via Digitalmars-d-learn]

Why isn't there an overload for `std.algorithm.sorting.sort` that 
takes a `unaryFun` lambda?

Something like
    x[].sort!"a.m";

sorting elements in `x` according to the value of element member 
`m` compared to the longer

    x[].sort!"a.m < b.m";