rollup merge of #21830: japaric/for-cleanup

Conflicts:
	src/librustc/metadata/filesearch.rs
	src/librustc_back/target/mod.rs
	src/libstd/os.rs
	src/libstd/sys/windows/os.rs
	src/libsyntax/ext/tt/macro_parser.rs
	src/libsyntax/print/pprust.rs
	src/test/compile-fail/issue-2149.rs

src/libsyntax/parse/mod.rs

@@ -1164,7 +1164,7 @@ mod test {
                     "impl z { fn a (self: Foo, &myarg: i32) {} }",
                     ];
 
-        for &src in srcs.iter() {
+        for &src in &srcs {
             let spans = get_spans_of_pat_idents(src);
             let Span{ lo, hi, .. } = spans[0];
             assert!("self" == &src[lo.to_usize()..hi.to_usize()],