Make natDisconnect() be called upon ext module deallocation (#211)

These changes make it so the natDisconnect() function is called for
you automatically if you forget it.  No effect in-process.

NatlinkSource/DragonCode.cpp

@@ -694,6 +694,13 @@ BOOL CDragonCode::isNatSpeakRunning()
 
 //---------------------------------------------------------------------------
 
+void CDragonCode::freeModule()
+{
+	natDisconnect();
+}
+
+//---------------------------------------------------------------------------
+
 void CDragonCode::releaseObjects()
 {
 	// iterate over all the grammar objects and free them; note that when we

NatlinkSource/DragonCode.h

@@ -114,6 +114,10 @@ class CDragonCode
 	void setAppClass( CDgnAppSupport * pAppClass ) { m_pAppClass = pAppClass; }
 	void setDuringInit( BOOL bState ) { m_bDuringInit = bState; }
 
+	// this is called when the natlink module (this class!) is deallocated from
+	// Python
+	void freeModule();
+
 	// these functions are called from CGrammarObject
 	ISRCentral * pISRCentral() { return m_pISRCentral; }
 	void addGramObj(CGrammarObject * pGramObj );

NatlinkSource/pythwrap.cpp

@@ -2317,16 +2317,28 @@ static struct PyMethodDef natlink_methods[] = {
 	{ NULL }
 };
 
+//---------------------------------------------------------------------------
+// natlink module free function.
+
+void natlink_free( void * p )
+{
+	cDragon.freeModule();
+}
+
 //---------------------------------------------------------------------------
 // import natlink from Python
 //
 // We tell Python about our functions and also create an error type.
 static struct PyModuleDef NatlinkModule = {
-		PyModuleDef_HEAD_INIT,
-		"_natlink_core",   /* name of module */
-		"natlink with python3 compatability",
-		-1,
-		natlink_methods
+		PyModuleDef_HEAD_INIT,                 /* m_base */
+		"_natlink_core",                       /* m_name */
+		"natlink with python3 compatability",  /* m_doc */
+		-1,                                    /* m_size */
+		natlink_methods,                       /* m_methods */
+		NULL,                                  /* m_slots */
+		NULL,                                  /* m_traverse */
+		NULL,                                  /* m_clear */
+		natlink_free                           /* m_free */
 };