Imitate support for suspend modifier on parameterless lambdas

#KT-22766 In Progress

compiler/testData/diagnostics/testsWithStdLib/coroutines/suspendLambda.kt

@@ -0,0 +1,20 @@
+import kotlin.coroutines.experimental.Continuation
+import kotlin.coroutines.experimental.CoroutineContext
+import kotlin.coroutines.experimental.startCoroutine
+
+fun bar() {
+    suspend {
+        println()
+    }.startCoroutine(object: Continuation<Unit> {
+        override val context: CoroutineContext
+            get() = TODO("not implemented")
+
+        override fun resume(value: Unit) {
+            TODO("not implemented")
+        }
+
+        override fun resumeWithException(exception: Throwable) {
+            TODO("not implemented")
+        }
+    })
+}

compiler/testData/diagnostics/testsWithStdLib/coroutines/suspendLambda.txt

@@ -0,0 +1,3 @@
+package
+
+public fun bar(): kotlin.Unit