Make builtin classes final. (#53)

runtime/src/main/kotlin/kotlin/Array.kt

@@ -2,7 +2,7 @@ package kotlin
 
 // TODO: remove that, as RTTI shall be per instantiation.
 @ExportTypeInfo("theArrayTypeInfo")
-class Array<T> : Cloneable {
+public final class Array<T> : Cloneable {
     // Constructors are handled with compiler magic.
     public constructor(@Suppress("UNUSED_PARAMETER") size: Int) {}
 

runtime/src/main/kotlin/kotlin/Boolean.kt

@@ -4,7 +4,7 @@ package kotlin
  * Represents a value which is either `true` or `false`. On the JVM, non-nullable values of this type are
  * represented as values of the primitive type `boolean`.
  */
-public class Boolean : Comparable<Boolean> {
+public final class Boolean : Comparable<Boolean> {
     /**
      * Returns the inverse of this boolean.
      */

runtime/src/main/kotlin/kotlin/Char.kt

@@ -4,7 +4,7 @@ package kotlin
  * Represents a 16-bit Unicode character.
  * On the JVM, non-nullable values of this type are represented as values of the primitive type `char`.
  */
-public class Char : Comparable<Char> {
+public final class Char : Comparable<Char> {
 
     /**
      * Compares this value with the specified value for order.

runtime/src/main/kotlin/kotlin/Nothing.kt

@@ -4,4 +4,4 @@ package kotlin
  * Nothing has no instances. You can use Nothing to represent "a value that never exists": for example,
  * if a function has the return type of Nothing, it means that it never returns (always throws an exception).
  */
-public class Nothing private constructor() {}
+public final class Nothing private constructor() {}

runtime/src/main/kotlin/kotlin/Primitives.kt

@@ -4,7 +4,7 @@ package kotlin
  * Represents a 8-bit signed integer.
  * On the JVM, non-nullable values of this type are represented as values of the primitive type `byte`.
  */
-public class Byte : Number(), Comparable<Byte> {
+public final class Byte : Number(), Comparable<Byte> {
     companion object {
         /**
          * A constant holding the minimum value an instance of Byte can have.
@@ -201,7 +201,7 @@ public class Byte : Number(), Comparable<Byte> {
  * Represents a 16-bit signed integer.
  * On the JVM, non-nullable values of this type are represented as values of the primitive type `short`.
  */
-public class Short : Number(), Comparable<Short> {
+public final class Short : Number(), Comparable<Short> {
     companion object {
         /**
          * A constant holding the minimum value an instance of Short can have.
@@ -398,7 +398,7 @@ public class Short : Number(), Comparable<Short> {
  * Represents a 32-bit signed integer.
  * On the JVM, non-nullable values of this type are represented as values of the primitive type `int`.
  */
-public class Int : Number(), Comparable<Int> {
+public final class Int : Number(), Comparable<Int> {
     companion object {
         /**
          * A constant holding the minimum value an instance of Int can have.
@@ -617,7 +617,7 @@ public class Int : Number(), Comparable<Int> {
  * Represents a 64-bit signed integer.
  * On the JVM, non-nullable values of this type are represented as values of the primitive type `long`.
  */
-public class Long : Number(), Comparable<Long> {
+public final class Long : Number(), Comparable<Long> {
     companion object {
         /**
          * A constant holding the minimum value an instance of Long can have.
@@ -836,7 +836,7 @@ public class Long : Number(), Comparable<Long> {
  * Represents a single-precision 32-bit IEEE 754 floating point number.
  * On the JVM, non-nullable values of this type are represented as values of the primitive type `float`.
  */
-public class Float : Number(), Comparable<Float> {
+public final class Float : Number(), Comparable<Float> {
     companion object {
         /**
          * A constant holding the smallest *positive* nonzero value of Float.
@@ -1040,7 +1040,7 @@ public class Float : Number(), Comparable<Float> {
  * Represents a double-precision 64-bit IEEE 754 floating point number.
  * On the JVM, non-nullable values of this type are represented as values of the primitive type `double`.
  */
-public class Double : Number(), Comparable<Double> {
+public final class Double : Number(), Comparable<Double> {
     companion object {
         /**
          * A constant holding the smallest *positive* nonzero value of Double.

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 {
+public final class String : Comparable<String>, CharSequence {
     @SymbolName("Kotlin_String_hashCode")
     external public override fun hashCode(): Int