Reorganize stdlib-js sources specific to the current JS backend

Move kotlin-stdlib-js project and the sources specific to the current backend to 'stdlib/js-v1' directory,
but leave sources that can be shared with the new IR backend in the common 'stdlib/js' location
with exception for 'stdlib/js/src/generated', which is used exclusively for current backend.
This simplifies sourceset configuration when building stdlib with the new backend.

libraries/stdlib/js-ir/runtime/coroutineInternalJS.kt

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+
+package kotlin.js
+
+import kotlin.js.coroutineAliases.*
+
+
+@PublishedApi
+internal fun <T> getContinuation(): ContinuationAlias<T> { throw Exception("Implemented as intrinsic") }
+// Do we really need this intrinsic in JS?
+
+@PublishedApi
+internal suspend fun <T> returnIfSuspended(@Suppress("UNUSED_PARAMETER") argument: Any?): T {
+    throw Exception("Implemented as intrinsic")
+}
+
+@PublishedApi
+internal fun <T> interceptContinuationIfNeeded(
+    context: CoroutineContextAlias,
+    continuation: ContinuationAlias<T>
+) = context[ContinuationInterceptorAlias]?.interceptContinuation(continuation) ?: continuation
+
+
+@SinceKotlin("1.2")
+@PublishedApi
+internal suspend fun getCoroutineContext(): CoroutineContextAlias = getContinuation<Any?>().context
+
+// TODO: remove `JS` suffix oncec `NameGenerator` is implemented
+@PublishedApi
+internal suspend fun <T> suspendCoroutineUninterceptedOrReturnJS(block: (ContinuationAlias<T>) -> Any?): T =
+    returnIfSuspended<T>(block(getContinuation<T>()))
+
+