Move FFI categories beneath Libraries instead of Dev Tools
Move FFI categories beneath Libraries instead of Dev Tools

rust-lang/crates.io,Susurrus/crates.io,Susurrus/crates.io,rust-lang/crates.io,rust-lang/crates.io,Susurrus/crates.io,Susurrus/crates.io,steveklabnik/crates.io,rust-lang/crates.io,steveklabnik/crates.io,steveklabnik/crates.io,steveklabnik/crates.io