Implement PartialEq between &str and OsString

Allows for example `os_string == "something"`

src/libstd/ffi/os_str.rs

@@ -417,6 +417,20 @@ impl PartialEq<OsString> for str {
     }
 }
 
+#[stable(feature = "rust1", since = "1.28.0")]
+impl<'a> PartialEq<&'a str> for OsString {
+    fn eq(&self, other: &&'a str) -> bool {
+        **self == **other
+    }
+}
+
+#[stable(feature = "rust1", since = "1.28.0")]
+impl<'a> PartialEq<OsString> for &'a str {
+    fn eq(&self, other: &OsString) -> bool {
+        **other == **self
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Eq for OsString {}