Cleanups

.../src/com/oracle/truffle/r/engine/interop/RFunctionMR.java

...com/oracle/truffle/r/nodes/builtin/base/UpdateSubstr.java

.../oracle/truffle/r/nodes/access/BaseWriteVariableNode.java

...e/truffle/r/nodes/access/WriteLocalFrameVariableNode.java

...e/truffle/r/nodes/access/WriteSuperFrameVariableNode.java

...uffle/r/nodes/access/variables/LocalReadVariableNode.java

...m/oracle/truffle/r/nodes/function/ClassHierarchyNode.java

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

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