add RAbstractAtomicVector interface

....nodes/src/com/oracle/truffle/r/nodes/ffi/AsCharNode.java

...des/src/com/oracle/truffle/r/nodes/ffi/AsIntegerNode.java

...des/src/com/oracle/truffle/r/nodes/ffi/AsLogicalNode.java

....nodes/src/com/oracle/truffle/r/nodes/ffi/AsRealNode.java

...c/com/oracle/truffle/r/runtime/data/RTypesFlatLayout.java

...e/truffle/r/runtime/data/model/RAbstractAtomicVector.java

.../truffle/r/runtime/data/model/RAbstractComplexVector.java

...e/truffle/r/runtime/data/model/RAbstractDoubleVector.java

...acle/truffle/r/runtime/data/model/RAbstractIntVector.java

.../truffle/r/runtime/data/model/RAbstractLogicalVector.java

...acle/truffle/r/runtime/data/model/RAbstractRawVector.java

...e/truffle/r/runtime/data/model/RAbstractStringVector.java