encapsulate RPromise evaluation, add evaluate in frame

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

com.oracle.truffle.r.native/lib/darwin/libRDerived.dylib

...om/oracle/truffle/r/nodes/builtin/base/EvalFunctions.java

.../src/com/oracle/truffle/r/nodes/function/PromiseNode.java

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

...e/src/com/oracle/truffle/r/runtime/data/RDataFactory.java

...ntime/src/com/oracle/truffle/r/runtime/data/RPromise.java