py: Add MICROPY_PY_ALL_SPECIAL_METHODS and __iadd__ special method under it.
diff --git a/py/mpconfig.h b/py/mpconfig.h
index b54bd65..e8c8fcc 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -376,6 +376,12 @@
 #define MICROPY_PY_BUILTINS_PROPERTY (1)
 #endif
 
+// Whether to support complete set of special methods
+// for user classes, otherwise only the most used
+#ifndef MICROPY_PY_ALL_SPECIAL_METHODS
+#define MICROPY_PY_ALL_SPECIAL_METHODS (0)
+#endif
+
 // Whether to support compile function
 #ifndef MICROPY_PY_BUILTINS_COMPILE
 #define MICROPY_PY_BUILTINS_COMPILE (0)