Cast pipeline related issues fixed in a batch of builtins

.../src/com/oracle/truffle/r/library/grid/GridFunctions.java

...brary/src/com/oracle/truffle/r/library/stats/BinDist.java

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

...ibrary/src/com/oracle/truffle/r/library/stats/Covcor.java

...ibrary/src/com/oracle/truffle/r/library/stats/Cutree.java

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

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

...om/oracle/truffle/r/library/stats/RandFunctionsNodes.java

...c/com/oracle/truffle/r/library/stats/SplineFunctions.java

...m/oracle/truffle/r/library/stats/StatsFunctionsNodes.java

...ruffle/r/nodes/builtin/casts/fluent/HeadPhaseBuilder.java

...le.r.runtime/src/com/oracle/truffle/r/runtime/RError.java

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

...racle/truffle/r/test/builtins/TestBuiltin_SplineCoef.java

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

...oracle/truffle/r/test/builtins/TestBuiltin_rmultinom.java

documentation/dev/casts.md