handle RS4Object as envir argument in get/get0

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

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

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

.../com/oracle/truffle/r/nodes/builtin/base/SetS4Object.java

...m/oracle/truffle/r/nodes/builtin/base/TraceFunctions.java

...in/src/com/oracle/truffle/r/nodes/builtin/base/Xtfrm.java

...e/truffle/r/nodes/builtin/base/fastpaths/GetFastPath.java

.../com/oracle/truffle/r/nodes/builtin/fastr/FastRTrace.java

....r.nodes/src/com/oracle/truffle/r/nodes/objects/AsS4.java

...src/com/oracle/truffle/r/nodes/objects/GetS4DataSlot.java

...ntime/src/com/oracle/truffle/r/runtime/data/RPromise.java

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

...c/com/oracle/truffle/r/test/builtins/TestBuiltin_get.java