make CfgExit relational NTA (without backlink so far)

reusablecfg/src/main/jastadd/SimpleCFG.jrag

@@ -120,7 +120,7 @@ aspect SimpleCFG {
   /**
    * The exit node in a filtered CFG.
    */
-  syn nta CfgExit BodyDecl.exit() = new CfgExit();
+  syn lazy CfgExit BodyDecl.exit() = new CfgExit();
 
   eq Block.entry() {
     if (getNumStmt() > 0) {
@@ -678,7 +678,7 @@ aspect SimpleCFG {
   eq BlockLambdaBody.entry() = new CfgEntry(getBlock().entry());
   eq ExprLambdaBody.entry() = new CfgEntry(getExpr().entry());
 
-  syn nta CfgExit LambdaBody.exit() = new CfgExit();
+  syn lazy CfgExit LambdaBody.exit() = new CfgExit();
 
   eq BlockLambdaBody.getBlock().follow() = exit();
   eq ExprLambdaBody.getExpr().follow() = exit();