Adapt to new std::os::$platform modules
Adapt to new std::os::$platform modules

In 1f5f76adc36082ec514a6cfa4ad2d7e6655a5253, OS-specific modules
in std:: were re-ordered. This change adapts to the new module layout.

cGuille/rust-url,cGuille/rust-url,nox/rust-url,servo/rust-url,nox/rust-url,servo/rust-url