Fix typo (privledge->privilege)

Author: Patrick McCann

src/libstd/env.rs

@@ -526,7 +526,7 @@ pub fn temp_dir() -> PathBuf {
 /// Ok("/home/alex/bar")
 /// ```
 ///
-/// This sort of behavior has been known to [lead to privledge escalation] when
+/// This sort of behavior has been known to [lead to privilege escalation] when
 /// used incorrectly, for example.
 ///
 /// [lead to privledge escalation]: http://securityvulns.com/Wdocument183.html