[GR-7423] Review Special Nodes.

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

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

...rc/com/oracle/truffle/r/nodes/builtin/base/MakeNames.java

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

...cle/truffle/r/nodes/builtin/base/infix/SpecialsUtils.java

.../oracle/truffle/r/nodes/builtin/base/infix/Subscript.java

...e/truffle/r/nodes/builtin/base/infix/UpdateSubscript.java

...src/com/oracle/truffle/r/runtime/data/RComplexVector.java

.../src/com/oracle/truffle/r/runtime/data/RDoubleVector.java

...ime/src/com/oracle/truffle/r/runtime/data/RIntVector.java

...src/com/oracle/truffle/r/runtime/data/RLogicalVector.java

...ime/src/com/oracle/truffle/r/runtime/data/RRawVector.java

.../src/com/oracle/truffle/r/runtime/data/RStringVector.java

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

...om/oracle/truffle/r/test/builtins/TestBuiltin_vector.java