use VectorAccess in CastDoubleNode

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

...cle/truffle/r/nodes/builtin/casts/PipelineToCastNode.java

.../com/oracle/truffle/r/nodes/unary/CastDoubleBaseNode.java

.../src/com/oracle/truffle/r/nodes/unary/CastDoubleNode.java

...le/truffle/r/runtime/data/nodes/FastPathVectorAccess.java

...le/truffle/r/runtime/data/nodes/SlowPathVectorAccess.java

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

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

.../com/oracle/truffle/r/test/builtins/TestMiscBuiltins.java

.../oracle/truffle/r/test/library/fastr/TestJavaInterop.java