Improve coroutines library layout

- Split CoroutinesLibrary into common and JVM parts
- Get rid of startCoroutine duplications
- Make suspendCoroutine implementation to be platform independent

libraries/stdlib/common/src/kotlin/CoroutinesH.kt

@@ -14,18 +14,6 @@ public header fun <R, T> (suspend R.() -> T).createCoroutine(
         completion: Continuation<T>
 ): Continuation<Unit>
 
-/**
- * Starts coroutine with receiver type [R] and result type [T].
- * This function creates and start a new, fresh instance of suspendable computation every time it is invoked.
- * The [completion] continuation is invoked when coroutine completes with result of exception.
- * An optional [dispatcher] may be specified to customise dispatch of continuations between suspension points inside the coroutine.
- */
-@SinceKotlin("1.1")
-public header fun <R, T> (suspend R.() -> T).startCoroutine(
-        receiver: R,
-        completion: Continuation<T>
-)
-
 /**
  * Creates coroutine without receiver and with result type [T].
  * This function creates a new, fresh instance of suspendable computation every time it is invoked.
@@ -38,25 +26,17 @@ public header fun <T> (suspend () -> T).createCoroutine(
         completion: Continuation<T>
 ): Continuation<Unit>
 
-/**
- * Starts coroutine without receiver and with result type [T].
- * This function creates and start a new, fresh instance of suspendable computation every time it is invoked.
- * The [completion] continuation is invoked when coroutine completes with result of exception.
- * An optional [dispatcher] may be specified to customise dispatch of continuations between suspension points inside the coroutine.
- */
-@SinceKotlin("1.1")
-@Suppress("UNCHECKED_CAST")
-public header fun <T> (suspend  () -> T).startCoroutine(
-        completion: Continuation<T>
-)
+@PublishedApi
+internal header class SafeContinuation<in T> : Continuation<T> {
+    internal constructor(delegate: Continuation<T>, initialResult: Any?)
 
-/**
- * Obtains the current continuation instance inside suspend functions and suspends
- * currently running coroutine.
- *
- * In this function both [Continuation.resume] and [Continuation.resumeWithException] can be used either synchronously in
- * the same stack-frame where suspension function is run or asynchronously later in the same thread or
- * from a different thread of execution. Repeated invocation of any resume function produces [IllegalStateException].
- */
-@SinceKotlin("1.1")
-public header inline suspend fun <T> suspendCoroutine(crossinline block: (Continuation<T>) -> Unit): T
+    @PublishedApi
+    internal constructor(delegate: Continuation<T>)
+
+    @PublishedApi
+    internal fun getResult(): Any?
+
+    override val context: CoroutineContext
+    override fun resume(value: T): Unit
+    override fun resumeWithException(exception: Throwable): Unit
+}