Get Isle building on MinGW32 (#63)

* Add MxUnknown100dc6b0::~MxUnknown100dc6b0 stub

* Declare destructor of MxOmni and MxTransitionManager in class

* inline attribute must go first

* Stub LegoState::Vtable0x14 for Act3State

* MxStreamer::VTable0x14 is not an override

* Stub MxEntity::Destroy for LegoState::Destroy

* Stub MxUnknown100dc6e0 for MxSoundManager

* ::ClassName and ::IsA are const methods

* methods in the class body don't need a namespace

* MxSoundManager subclasses MxUnknown100dc6e0

* LegoInputManager subclasses MxPresenter

* NotificationId is an enum, and does not need __declspec(dllexport)

* Fix final #endif of legoomni.h and mxobjectfactory.h

* Add const alternative for LegoOmni::Create and MxVideoParam, only available for MinGW

* Alternative approach to MinGW compatibility

* MinGW on Linux is case sensitve

* Don't delete a member variable. C++ automatically destructs member variables

---------

Co-authored-by: MattKC <34096995+itsmattkc@users.noreply.github.com>

LEGO1/mxunknown100dc6e0.h

@@ -0,0 +1,19 @@
+#ifndef MXUNKNOWN100DC6E0_H
+#define MXUNKNOWN100DC6E0_H
+
+#include "mxunknown100dc6b0.h"
+
+// VTABLE 0x100dc6e0
+class MxUnknown100dc6e0 : public MxUnknown100dc6b0
+{
+public:
+  MxUnknown100dc6e0();
+  virtual ~MxUnknown100dc6e0() override;
+
+protected:
+  void Init();
+
+  int m_unk2c;
+};
+
+#endif // MXUNKNOWN100DC6E0_H