Implement coroutineContext intrinsic

This intrinsic allows coroutine to access its context without suspention
and, furthermore, disabling tail-call optimization.
KT-17609: Fixed

libraries/stdlib/src/kotlin/coroutines/experimental/intrinsics/Intrinsics.kt

@@ -45,6 +45,19 @@ import kotlin.coroutines.experimental.processBareContinuationResume
 public inline suspend fun <T> suspendCoroutineOrReturn(crossinline block: (Continuation<T>) -> Any?): T =
         throw NotImplementedError("Implementation is intrinsic")
 
+/**
+ * Continuation context of current coroutine.
+ *
+ * This allows the user code to not pass an extra [CoroutineContext] parameter in basic coroutine builders like [launch] and [async],
+ * but still provide easy access to coroutine context.
+ */
+@SinceKotlin("1.2")
+@Suppress("WRONG_MODIFIER_TARGET")
+public inline suspend val coroutineContext: CoroutineContext
+    get() {
+        throw NotImplementedError("Implemented as intrinsic")
+    }
+
 /**
  * This value is used as a return value of [suspendCoroutineOrReturn] `block` argument to state that
  * the execution was suspended and will not return any result immediately.