Rewritten conversion builtins to avoid copy on identity conversion.

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

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

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

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

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

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

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

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

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

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

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

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

...des/src/com/oracle/truffle/r/nodes/unary/CastRawNode.java

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