Use `clang::Type::is_valid` instead of checking self.kind() against CXType_Invalid
Use `clang::Type::is_valid` instead of checking self.kind() against CXType_Invalid

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