Bring back std::std, the curious inner-module did nothing wrong

https://github.com/rust-lang/rust/blob/0d3bd7720c50e3ada4bac77331d43926493be4fe/src/libstd/lib.rs#L273-L277

@Gankra it was one improvement rust had over c++. c++ never had std::std

@Gankra such a double standard

@dramforever ty dram you're an absolute treasure

@Gankra I have absolutely considered committing name-interception crimes against someone else’s macros. It’s good to know I can cite precedent.

@jrose unfortunately $crate killed rust's beautiful child :(