D3D11: silence null conversion warnings

Author: paroj

RenderSystems/Direct3D11/src/OgreD3D11HLSLProgram.cpp

@@ -317,7 +317,7 @@ namespace Ogre {
             mEntryPoint.c_str(),  // [in] Name of the shader-entrypoint function where shader execution begins. 
             target,               // [in] A string that specifies the shader model; can be any profile in shader model 4 or higher. 
             compileFlags,         // [in] Effect compile flags - no D3DCOMPILE_ENABLE_BACKWARDS_COMPATIBILITY at the first try...
-            NULL,                 // [in] Effect compile flags
+            0,                    // [in] Effect compile flags
             pMicroCode.GetAddressOf(),// [out] A pointer to an ID3DBlob Interface which contains the compiled shader, as well as any embedded debug and symbol-table information. 
             errors.GetAddressOf() // [out] A pointer to an ID3DBlob Interface which contains a listing of errors and warnings that occurred during compilation. These errors and warnings are identical to the the debug output from a debugger.
             );

RenderSystems/Direct3D11/src/OgreD3D11RenderSystem.cpp

@@ -2518,7 +2518,7 @@ namespace Ogre
                 { 4, 0 },  // MSAA 4x
                 { 2, 0 },  // MSAA 2x
                 { 1, 0 },  // MSAA 1x
-                { NULL },
+                { 0 },
         };
 
         // Find matching AA mode

RenderSystems/Direct3D11/src/OgreD3D11RenderWindow.cpp

@@ -812,7 +812,7 @@ namespace Ogre
 
         _createSwapChain();
         _createSizeDependedD3DResources();
-        mDevice.GetDXGIFactory()->MakeWindowAssociation(mHWnd, NULL);
+        mDevice.GetDXGIFactory()->MakeWindowAssociation(mHWnd, 0);
         setHidden(mHidden);
 
         D3D11RenderSystem* rsys = static_cast<D3D11RenderSystem*>(Root::getSingleton().getRenderSystem());
@@ -834,7 +834,7 @@ namespace Ogre
     void D3D11RenderWindowHwnd::notifyDeviceRestored(D3D11Device* device)
     {
         D3D11RenderWindowSwapChainBased::notifyDeviceRestored(device);
-        mDevice.GetDXGIFactory()->MakeWindowAssociation(mHWnd, NULL);
+        mDevice.GetDXGIFactory()->MakeWindowAssociation(mHWnd, 0);
     }
     //---------------------------------------------------------------------
 	HRESULT D3D11RenderWindowHwnd::_createSwapChainImpl(IDXGIDeviceN* pDXGIDevice)