Instead of verifying that the container of an 'invoke' is a
FunctionClassDescriptor instance, make sure that it's a function class
checking its FQ name instead (classId + isBuiltinFunctionClass calls).
This makes sure that we will create synthesized invokes in a setting
where function classes are not FunctionClassDescriptor instances
synthesized by the compiler, but ordinary classes from sources or
binaries as well, as is going to be the case in kotlin-native
Alexander Udalov
9f2ce3c521