unify access modifiers for guards

.../src/com/oracle/truffle/r/nodes/builtin/base/Combine.java

...racle/truffle/r/nodes/builtin/base/PrettyPrinterNode.java

...c/com/oracle/truffle/r/nodes/builtin/base/UpdateDiag.java

.../com/oracle/truffle/r/nodes/access/ArrayPositionCast.java

...com/oracle/truffle/r/nodes/access/VectorPositionCast.java

...m/oracle/truffle/r/nodes/binary/BinaryArithmeticNode.java

.../com/oracle/truffle/r/nodes/binary/BinaryBooleanNode.java

...ruffle/r/nodes/binary/BinaryBooleanNonVectorizedNode.java