Improve GC finalisation code; add option to disable it.
diff --git a/py/mpconfig.h b/py/mpconfig.h
index 65577f0..22724c8 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -55,6 +55,11 @@
#define MICROPY_ENABLE_GC (0)
#endif
+// Whether to enable finalisers in the garbage collector (ie call __del__)
+#ifndef MICROPY_ENABLE_GC_FINALISER
+#define MICROPY_ENABLE_GC_FINALISER (0)
+#endif
+
// Whether to include REPL helper function
#ifndef MICROPY_ENABLE_REPL_HELPERS
#define MICROPY_ENABLE_REPL_HELPERS (0)