Move sequence interface definition to a separate file.

Merge SequnceJVM content into Sequences.

libraries/stdlib/src/kotlin/collections/Sequence.kt

@@ -0,0 +1,14 @@
+package kotlin
+
+/**
+ * A sequence that returns values through its iterator. The values are evaluated lazily, and the sequence
+ * is potentially infinite.
+ *
+ * @param T the type of elements in the sequence.
+ */
+public interface Sequence<out T> {
+    /**
+     * Returns an iterator that returns the values from the sequence.
+     */
+    public operator fun iterator(): Iterator<T>
+}

libraries/stdlib/src/kotlin/collections/SequenceJVM.kt

@@ -1,17 +0,0 @@
-@file:kotlin.jvm.JvmMultifileClass
-@file:kotlin.jvm.JvmName("SequencesKt")
-
-package kotlin
-
-import java.util.concurrent.atomic.AtomicReference
-
-
-internal class ConstrainedOnceSequence<T>(sequence: Sequence<T>) : Sequence<T> {
-    private val sequenceRef = AtomicReference(sequence)
-
-    override fun iterator(): Iterator<T> {
-        val sequence = sequenceRef.getAndSet(null) ?: throw IllegalStateException("This sequence can be consumed only once.")
-        return sequence.iterator()
-    }
-}
-

libraries/stdlib/src/kotlin/collections/Sequences.kt

@@ -6,18 +6,7 @@ package kotlin
 import java.util.*
 import kotlin.support.AbstractIterator
 
-/**
- * A sequence that returns values through its iterator. The values are evaluated lazily, and the sequence
- * is potentially infinite.
- *
- * @param T the type of elements in the sequence.
- */
-public interface Sequence<out T> {
-    /**
-     * Returns an iterator that returns the values from the sequence.
-     */
-    public operator fun iterator(): Iterator<T>
-}
+
 
 /**
  * Creates a sequence that returns all elements from this iterator. The sequence is constrained to be iterated only once.
@@ -485,6 +474,18 @@ public fun <T> Sequence<T>.constrainOnce(): Sequence<T> {
     return if (this is ConstrainedOnceSequence<T>) this else ConstrainedOnceSequence(this)
 }
 
+@kotlin.jvm.JvmVersion
+private class ConstrainedOnceSequence<T>(sequence: Sequence<T>) : Sequence<T> {
+    private val sequenceRef = java.util.concurrent.atomic.AtomicReference(sequence)
+
+    override fun iterator(): Iterator<T> {
+        val sequence = sequenceRef.getAndSet(null) ?: throw IllegalStateException("This sequence can be consumed only once.")
+        return sequence.iterator()
+    }
+}
+
+
+
 /**
  * Returns a sequence which invokes the function to calculate the next value on each iteration until the function returns `null`.
  *