combine builtin removes attributes

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

...time/src/com/oracle/truffle/r/runtime/data/RSequence.java

...untime/src/com/oracle/truffle/r/runtime/data/RVector.java

...cle/truffle/r/runtime/data/closures/RToVectorClosure.java

.../oracle/truffle/r/runtime/data/model/RAbstractVector.java

...est/src/com/oracle/truffle/r/test/ExpectedTestOutput.test

...le.r.test/src/com/oracle/truffle/r/test/all/AllTests.java

.../com/oracle/truffle/r/test/simple/TestSimpleBuiltins.java