introduce OperatorNode as baseclass for special nodes masquerading as calls

...e.r.nodes/src/com/oracle/truffle/r/nodes/RASTBuilder.java

.../com/oracle/truffle/r/nodes/control/AbstractLoopNode.java

...des/src/com/oracle/truffle/r/nodes/control/BlockNode.java

...des/src/com/oracle/truffle/r/nodes/control/BreakNode.java

...nodes/src/com/oracle/truffle/r/nodes/control/ForNode.java

....nodes/src/com/oracle/truffle/r/nodes/control/IfNode.java

...odes/src/com/oracle/truffle/r/nodes/control/NextNode.java

.../src/com/oracle/truffle/r/nodes/control/OperatorNode.java

...es/src/com/oracle/truffle/r/nodes/control/RepeatNode.java

...acle/truffle/r/nodes/control/ReplacementDispatchNode.java

...des/src/com/oracle/truffle/r/nodes/control/WhileNode.java

...racle/truffle/r/nodes/function/signature/MissingNode.java