Add From<&Self> implementations for HeaderValue, Method, and Status (#238)

Parallels bccac1427a

src/header/value.rs

@@ -485,6 +485,13 @@ impl From<HeaderValue> for Bytes {
     }
 }
 
+impl<'a> From<&'a HeaderValue> for HeaderValue {
+    #[inline]
+    fn from(t: &'a HeaderValue) -> Self {
+        t.clone()
+    }
+}
+
 impl<'a> HttpTryFrom<&'a HeaderValue> for HeaderValue {
     type Error = ::error::Never;
 

src/method.rs

@@ -336,6 +336,13 @@ impl Default for Method {
     }
 }
 
+impl<'a> From<&'a Method> for Method {
+    #[inline]
+    fn from(t: &'a Method) -> Self {
+        t.clone()
+    }
+}
+
 impl<'a> HttpTryFrom<&'a Method> for Method {
     type Error = ::error::Never;
 

src/status.rs

@@ -241,6 +241,13 @@ impl FromStr for StatusCode {
     }
 }
 
+impl<'a> From<&'a StatusCode> for StatusCode {
+    #[inline]
+    fn from(t: &'a StatusCode) -> Self {
+        t.clone()
+    }
+}
+
 impl<'a> HttpTryFrom<&'a StatusCode> for StatusCode {
     type Error = ::error::Never;