introduce optimized visibility handling

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

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

...acle/truffle/r/nodes/function/FunctionDefinitionNode.java

...ruffle/r/nodes/function/call/CallRFunctionCachedNode.java

...acle/truffle/r/nodes/function/call/CallRFunctionNode.java

...ruffle/r/nodes/function/visibility/GetVisibilityNode.java

...ruffle/r/nodes/function/visibility/SetVisibilityNode.java

...untime/src/com/oracle/truffle/r/runtime/FastROptions.java

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

...rc/com/oracle/truffle/r/runtime/env/frame/RFrameSlot.java

...est/src/com/oracle/truffle/r/test/tck/FastRDebugTest.java