Added startsWith().

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4301 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/as/com/threerings/util/StringUtil.as

@@ -34,6 +34,15 @@ public class StringUtil
         return (startDex >= 0) && (str.indexOf(substr, startDex) >= 0);
     }
 
+    /**
+     * Does the specified string start with the specified substring.
+     */
+    public static function startsWith (str :String, substr :String) :Boolean
+    {
+        // just check once if it's at the beginning
+        return (str.lastIndexOf(substr, 0) == 0);
+    }
+
     /**
      * Utility function that strips whitespace from the ends of a String.
      */