Add a with-scope so that optimize-tree doesn't pollute namespace

basis/compiler/tree/optimizer/optimizer.factor

@@ -25,6 +25,7 @@ SYMBOL: check-optimizer?
     ] when ;
 
 : optimize-tree ( nodes -- nodes' )
+    [
         analyze-recursive
         normalize
         propagate
@@ -39,4 +40,5 @@ SYMBOL: check-optimizer?
         ?check
         compute-def-use
         optimize-modular-arithmetic
-    finalize ;
+        finalize
+    ] with-scope ;