only use RRuntime.asAbstractVector where necessary

...src/com/oracle/truffle/r/engine/TruffleRLanguageImpl.java

...com/oracle/truffle/r/ffi/impl/nodes/CoerceVectorNode.java

...src/com/oracle/truffle/r/library/stats/CompleteCases.java

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

...acle/truffle/r/nodes/builtin/base/DatePOSIXFunctions.java

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

...n/src/com/oracle/truffle/r/nodes/builtin/base/VApply.java

...cle/truffle/r/nodes/builtin/base/printer/ListPrinter.java

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

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

...s/src/com/oracle/truffle/r/nodes/builtin/CastBuilder.java

...le/truffle/r/nodes/function/ClassHierarchyScalarNode.java

...odes/src/com/oracle/truffle/r/nodes/unary/TypeofNode.java

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

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

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