Auto merge of #682 - fitzgen:bump-clang-sys-version, r=upsuper
Auto merge of #682 - fitzgen:bump-clang-sys-version, r=upsuper

Bump the required clang-sys version to 0.15.2

Better fix for #671 for downstream crates.

r? @upsuper or @emilio

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