Stop testing libclang 3.7
Stop testing libclang 3.7

No one intends to make this work. We should focus on new versions of libclang
going forward.

emilio/rust-bindgen,emilio/rust-bindgen,emilio/rust-bindgen,emilio/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen,emilio/rust-bindgen