refactor(lib): use type macro to detect impl Trait

build.rs

@@ -2,13 +2,12 @@ extern crate rustc_version;
 use rustc_version::{version, Version};
 
 fn main() {
-
     // Check for a minimum version to see if new rust features can be used
     let version = version().unwrap();
     if version >= Version::parse("1.26.0").unwrap() {
-        println!("cargo:rustc-cfg=impl_trait_available");
+        println!("cargo:rustc-cfg=__hyper_impl_trait_available");
     }
     if version >= Version::parse("1.23.0").unwrap() {
-        println!("cargo:rustc-cfg=inherent_ascii");
+        println!("cargo:rustc-cfg=__hyper_inherent_ascii");
     }
 }