don't use stable frame slot assumptions for function frames

...fle.r.engine/src/com/oracle/truffle/r/engine/REngine.java

...nodes/src/com/oracle/truffle/r/nodes/RTruffleVisitor.java

.../src/com/oracle/truffle/r/nodes/builtin/RBuiltinNode.java

....r.runtime/src/com/oracle/truffle/r/runtime/RRuntime.java

...e/truffle/r/runtime/env/frame/FrameSlotChangeMonitor.java

...le/truffle/r/runtime/env/frame/REnvMaterializedFrame.java