Ensure that a copy of a DIB wxBitmap remains a DIB in wxMSW

Creating a DDB from DIB with alpha doesn't work correctly due to using
premultiplied alpha for the latter, but not for the former, and while we
could convert it, it seems to be even better to just preserve the type
of the original bitmap, as this would seem to be expected when making a
copy, after all.

This commit is best viewed ignoring whitespace-only changes.

src/msw/bitmap.cpp

@@ -232,6 +232,21 @@ wxBitmapRefData::wxBitmapRefData(const wxBitmapRefData& data)
     if ( data.m_hBitmap )
     {
         wxDIB dib((HBITMAP)(data.m_hBitmap));
+
+        // Cloning a DIB should create a DIB, while cloning a DDB should create
+        // a DDB, so check what do we have.
+        if ( data.m_isDIB )
+        {
+            const int w = dib.GetWidth();
+            const int h = dib.GetHeight();
+            const int d = dib.GetDepth();
+
+            wxDIB dibDst(w, h, d);
+            memcpy(dibDst.GetData(), dib.GetData(), wxDIB::GetLineSize(w, d)*h);
+            InitFromDIB(dibDst);
+        }
+        else
+        {
             // DDB obtained from CopyFromDIB() can have different
             // colour depth than source DIB so we need to check it.
             CopyFromDIB(dib);
@@ -253,6 +268,7 @@ wxBitmapRefData::wxBitmapRefData(const wxBitmapRefData& data)
                 }
             }
         }
+    }
 #endif // wxUSE_WXDIB
 
     // Ensure this is done after the block above otherwise if the color depth didn't match we'll lose the mask