Make read_userroot a JIT intrinsic

kernel/modelverse_jit/intrinsics.py

@@ -205,6 +205,13 @@ MISC_INTRINSICS = {
             tree_ir.LoadLocalInstruction(jit.KWARGS_PARAMETER_NAME),
             tree_ir.LiteralInstruction('root')),
 
+    # # read_userroot
+    'read_userroot' :
+        lambda:
+        tree_ir.LoadIndexInstruction(
+            tree_ir.LoadLocalInstruction(jit.KWARGS_PARAMETER_NAME),
+            tree_ir.LiteralInstruction('user_root')),
+
     # Dictionary operations
     'dict_read' :
         lambda a, b: