std: Clean out #[deprecated] APIs

This commit cleans out a large amount of deprecated APIs from the standard
library and some of the facade crates as well, updating all users in the
compiler and in tests as it goes along.

src/libstd/path.rs

@@ -1318,7 +1318,7 @@ impl Path {
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn file_name(&self) -> Option<&OsStr> {
         self.components().next_back().and_then(|p| match p {
-            Component::Normal(p) => Some(p.as_os_str()),
+            Component::Normal(p) => Some(p.as_ref()),
             _ => None
         })
     }