Support open suspend members and super-calls

The problem was that the resume call (from doResume) for open members
was based on common INVOKEVIRTUAL to the original function
that lead to the invocation of the override when it was expected
to be the overridden (after super-call being suspended)

The solution is to generate method bodies for open members into
the special $suspendImpl synthetic function that may be called
from the doResume implementation

 #KT-17587 Fixed

core/descriptors/src/org/jetbrains/kotlin/descriptors/descriptorUtil.kt

@@ -19,6 +19,7 @@ package org.jetbrains.kotlin.descriptors
 import org.jetbrains.kotlin.incremental.components.LookupLocation
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.resolve.DescriptorUtils
+import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 import org.jetbrains.kotlin.utils.sure
 
 fun ModuleDescriptor.resolveClassByFqName(fqName: FqName, lookupLocation: LookupLocation): ClassDescriptor? {
@@ -37,3 +38,6 @@ fun ModuleDescriptor.findContinuationClassDescriptorOrNull(lookupLocation: Looku
 
 fun ModuleDescriptor.findContinuationClassDescriptor(lookupLocation: LookupLocation) =
         findContinuationClassDescriptorOrNull(lookupLocation).sure { "Continuation interface is not found" }
+
+fun FunctionDescriptor.isEffectivelyOpen() =
+        modality == Modality.OPEN && containingDeclaration.safeAs<ClassDescriptor>()?.modality == Modality.OPEN