Add freevars and cellvars extraction

Author: msimacek

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/code/PCode.java

@@ -189,6 +189,8 @@ private static Set<Object> asSet(Object[] objects) {
     private static String[] extractFreeVars(RootNode rootNode) {
         if (rootNode instanceof PClosureRootNode) {
             return ((PClosureRootNode) rootNode).getFreeVars();
+        } else if (rootNode instanceof PBytecodeRootNode) {
+            return ((PBytecodeRootNode) rootNode).getCodeUnit().freevars;
         } else {
             return PythonUtils.EMPTY_STRING_ARRAY;
         }
@@ -197,6 +199,8 @@ private static String[] extractFreeVars(RootNode rootNode) {
     private static String[] extractCellVars(RootNode rootNode) {
         if (rootNode instanceof PClosureFunctionRootNode) {
             return ((PClosureFunctionRootNode) rootNode).getCellVars();
+        } else if (rootNode instanceof PBytecodeRootNode) {
+            return ((PBytecodeRootNode) rootNode).getCodeUnit().cellvars;
         } else {
             return PythonUtils.EMPTY_STRING_ARRAY;
         }