[GR-2738] Improvements for NetBeans debugger.

...rc/com/oracle/truffle/r/engine/RRuntimeASTAccessImpl.java

...ine/src/com/oracle/truffle/r/engine/TruffleRLanguage.java

...ine/src/com/oracle/truffle/r/engine/interop/REmptyMR.java

...e/truffle/r/engine/interop/RForeignAccessFactoryImpl.java

...e/src/com/oracle/truffle/r/engine/interop/RMissingMR.java

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

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

...tin/src/com/oracle/truffle/r/nodes/builtin/base/DPut.java

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

...truffle/r/nodes/builtin/base/printer/LanguagePrinter.java

...e/truffle/r/nodes/builtin/base/printer/SymbolPrinter.java

...oracle/truffle/r/nodes/builtin/fastr/FastRSourceInfo.java

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

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

....runtime/src/com/oracle/truffle/r/runtime/env/RScope.java