provide interop access to R vectors and functions

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

...com/oracle/truffle/r/engine/interop/ConstantRootNode.java

...ruffle/r/engine/interop/RAbstractVectorAccessFactory.java

...acle/truffle/r/engine/interop/RFunctionAccessFactory.java

.../oracle/truffle/r/engine/interop/RInteropExecuteNode.java

...c/com/oracle/truffle/r/engine/interop/VectorReadNode.java

...c/com/oracle/truffle/r/engine/interop/VectorSizeNode.java

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

...time/src/com/oracle/truffle/r/runtime/data/RFunction.java

.../oracle/truffle/r/runtime/data/model/RAbstractVector.java