Add runtime function for string to array conversion.

src/string.js

Index: src/string.js
diff --git a/src/string.js b/src/string.js
index 531c6a9b949bbb4c897c761926fcd9164cbbb024..067578c1414d0e422e17b19354f9ae1497b69304 100644
--- a/src/string.js
+++ b/src/string.js
@@ -530,11 +530,7 @@ function StringSplit(separator, limit) {
     var separator_length = separator.length;
 
     // If the separator string is empty then return the elements in the subject.
-    if (separator_length === 0) {
-      var result = $Array(length);
-      for (var i = 0; i < length; i++) result[i] = subject[i];
-      return result;
-    }
+    if (separator_length === 0) return %StringToArray(subject);
 
     var result = [];
     var start_index = 0;