add @TruffleBoundary to REngine.transform

com.oracle.truffle.r.engine/src/com/oracle/truffle/r/engine/REngine.java

@@ -453,6 +453,7 @@ final class REngine implements Engine, Engine.Timings {
      * @param astNode parser AST instance
      * @return the root node of the Truffle AST
      */
+    @TruffleBoundary
     private static RSyntaxNode transform(ASTNode astNode) {
         return new RTruffleVisitor().transform(astNode);
     }
@@ -464,8 +465,8 @@ final class REngine implements Engine, Engine.Timings {
     }
 
     /**
-     * Creates an anonymous function, with no arguments to evaluate {@code body}. If {@body} is a
-     * not a syntax node, uses a simple {@link BodyNode} with no source information. Otherwise
+     * Creates an anonymous function, with no arguments to evaluate {@code body}. If {@body}
+     * is a not a syntax node, uses a simple {@link BodyNode} with no source information. Otherwise
      * creates a {@link FunctionStatementsNode} using {@code body}. and ensures that the
      * {@link FunctionBodyNode} has a {@link SourceSection}, for instrumentation, although the
      * anonymous {@link FunctionDefinitionNode} itself does not need one.