Python 3.9 support for -builtin

Add missing initializer for member ‘_heaptypeobject::ht_module’ to complete
Python 3.9 support.

CHANGES.current

@@ -7,6 +7,10 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.1.0 (in progress)
 ===========================
 
+2020-08-16: wsfulton
+            [Python] Add missing initializer for member ‘_heaptypeobject::ht_module’ when using
+            -builtin to complete Python 3.9 support.
+
 2020-08-16: wsfulton
             [Python] Remove PyEval_InitThreads() call for Python 3.7 and later as Python calls
             it automatically now. This removes a deprecation warning when using Python 3.9.

Source/Modules/python.cxx

@@ -4308,6 +4308,10 @@ public:
     // struct _dictkeysobject *ht_cached_keys;
     printSlot(f, getSlot(n, "feature:python:ht_cached_keys"), "ht_cached_keys");
     Printv(f, "#endif\n", NIL);
+
+    Printv(f, "#if PY_VERSION_HEX >= 0x03090000\n", NIL);
+    printSlot(f, getSlot(n, "feature:python:ht_module"), "ht_module", "PyObject *");
+    Printv(f, "#endif\n", NIL);
     Printf(f, "};\n\n");
 
     String *clientdata = NewString("");