[vim keymap] IE7-proof a loop over a string

keymap/vim.js

@@ -503,9 +503,9 @@
     setupPrefixBindingForKey(toCombo(ch));
     setupPrefixBindingForKey(toCombo(ch.toLowerCase()));
   }
-  iterList(SPECIAL_SYMBOLS, function (ch) {
-    setupPrefixBindingForKey(toCombo(ch));
-  });
+  for (var i = 0; i < SPECIAL_SYMBOLS.length; ++i) {
+    setupPrefixBindingForKey(toCombo(SPECIAL_SYMBOLS.charAt(i)));
+  }
   setupPrefixBindingForKey("Space");
 
   CodeMirror.keyMap["vim-prefix-y"] = {