Convert old-style for loops to new-style

Most could use the each method, but because of the hack used to
disambiguate old- and new-style loops, some had to use vec::each.

(This hack will go away soon.)

Issue #1619

src/libcore/vec.rs

@@ -62,7 +62,7 @@ export zip;
 export swap;
 export reverse;
 export reversed;
-export iter, each, eachi;
+export iter, iter_between, each, eachi;
 export iter2;
 export iteri;
 export riter;