Make String CharSequence compatible.

runtime/src/main/kotlin/kotlin/String.kt

@@ -4,7 +4,7 @@ package kotlin
 external fun fromUtf8Array(array: ByteArray) : String
 
 @ExportTypeInfo("theStringTypeInfo")
-class String : Comparable<String>/* , CharSequence */ {
+class String : Comparable<String>, CharSequence {
     @SymbolName("Kotlin_String_hashCode")
     external public override fun hashCode(): Int
 
@@ -13,20 +13,19 @@ class String : Comparable<String>/* , CharSequence */ {
         return plusImpl(other.toString())
     }
 
-    /*
-    public fun override toString(): String {
+    override public fun toString(): String {
         return this
-    } */
+    }
 
-    public /* override */ val length: Int
+    public override val length: Int
         get() = getStringLength()
 
     // Can be O(N).
     @SymbolName("Kotlin_String_get")
-    external /* override */ public fun get(index: Int): Char
+    external override public fun get(index: Int): Char
 
     @SymbolName("Kotlin_String_subSequence")
-    external /* override */ public fun subSequence(startIndex: Int, endIndex: Int): CharSequence
+    external override public fun subSequence(startIndex: Int, endIndex: Int): CharSequence
 
     @SymbolName("Kotlin_String_compareTo")
     override external public fun compareTo(other: String): Int
@@ -35,7 +34,7 @@ class String : Comparable<String>/* , CharSequence */ {
     external private fun getStringLength(): Int
 
     @SymbolName("Kotlin_String_plusImpl")
-    external private fun plusImpl(other:Any): String
+    external private fun plusImpl(other: Any): String
 
     @SymbolName("Kotlin_String_equals")
     external public override fun equals(other: Any?): Boolean