[WASM] Initial runtime library

Add directory libraries/stdlib/wasm as a placeholder for WASM runtime library
Copy built-ins from core/builtins
Add ExcludeFromCodegen annotation for internal needs

libraries/stdlib/wasm/builtins/native/kotlin/Array.kt

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+@file:Suppress(
+    "NON_ABSTRACT_FUNCTION_WITH_NO_BODY",
+    "MUST_BE_INITIALIZED_OR_BE_ABSTRACT",
+    "EXTERNAL_TYPE_EXTENDS_NON_EXTERNAL_TYPE",
+    "PRIMARY_CONSTRUCTOR_DELEGATION_CALL_EXPECTED",
+    "WRONG_MODIFIER_TARGET"
+)
+
+package kotlin
+
+/**
+ * Represents an array (specifically, a Java array when targeting the JVM platform).
+ * Array instances can be created using the [arrayOf], [arrayOfNulls] and [emptyArray]
+ * standard library functions.
+ * See [Kotlin language documentation](https://kotlinlang.org/docs/reference/basic-types.html#arrays)
+ * for more information on arrays.
+ */
+public class Array<T> {
+    /**
+     * Creates a new array with the specified [size], where each element is calculated by calling the specified
+     * [init] function.
+     *
+     * The function [init] is called for each array element sequentially starting from the first one.
+     * It should return the value for an array element given its index.
+     */
+    public inline constructor(size: Int, init: (Int) -> T)
+
+    /**
+     * Returns the array element at the specified [index]. This method can be called using the
+     * index operator.
+     * ```
+     * value = arr[index]
+     * ```
+     *
+     * If the [index] is out of bounds of this array, throws an [IndexOutOfBoundsException] except in Kotlin/JS
+     * where the behavior is unspecified.
+     */
+    public operator fun get(index: Int): T
+
+    /**
+     * Sets the array element at the specified [index] to the specified [value]. This method can
+     * be called using the index operator.
+     * ```
+     * arr[index] = value
+     * ```
+     *
+     * If the [index] is out of bounds of this array, throws an [IndexOutOfBoundsException] except in Kotlin/JS
+     * where the behavior is unspecified.
+     */
+    public operator fun set(index: Int, value: T): Unit
+
+    /**
+     * Returns the number of elements in the array.
+     */
+    public val size: Int
+
+    /**
+     * Creates an iterator for iterating over the elements of the array.
+     */
+    public operator fun iterator(): Iterator<T>
+}