fix various warnings
rustc: capitalize types in rscope.rs
std: Add a fixme for when we add Trait::<for T>::static_method()
auto merge of #8889 : erickt/rust/cleanup, r=catamorphism

This fixes a couple minor things I've been sitting on. It cleans up some warnings, CapCases some types in librustc's rscope module, and adds a fixme.