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/mxentity.h

@@ -23,6 +23,8 @@ public:
     return !strcmp(name, MxEntity::ClassName()) || MxCore::IsA(name);
   }
 
+  virtual void Destroy(); // vtable+0x1c
+
   // 0x8: MxResult
   // 0xc MxAtomId
 };