Typed Memory Objects missing from `core.sys.posix.sys.mman`

It appears as though Typed Memory Objects are [intended to have bindings in mman.d](https://github.com/dlang/dmd/blob/master/druntime/src/core/sys/posix/sys/mman.d#L836); but there are no bindings, only a documentation header. Actual bindings for these would be really useful.