vtkWin32OpenGLRenderWindow: avoid narrowing warnings

The array is of BYTE, but there are some integers floating around.
Static cast them to BYTEs.

Change-Id: I6ff0ae85a78908fdcb3fb9df45bb5e8d5efca2da

Rendering/OpenGL/vtkWin32OpenGLRenderWindow.cxx

@@ -678,19 +678,21 @@ void vtkWin32OpenGLRenderWindow::SetupPixelFormat(HDC hDC, DWORD dwFlags,
     return;
     }
 
+  BYTE bpp_byte = static_cast<BYTE>(bpp);
+  BYTE zbpp_byte = static_cast<BYTE>(zbpp);
   PIXELFORMATDESCRIPTOR pfd = {
     sizeof(PIXELFORMATDESCRIPTOR),  /* size */
     1,                              /* version */
     dwFlags         ,               /* support double-buffering */
     PFD_TYPE_RGBA,                  /* color type */
-    bpp,                             /* preferred color depth */
+    bpp_byte,                       /* preferred color depth */
     0, 0, 0, 0, 0, 0,               /* color bits (ignored) */
-    this->AlphaBitPlanes ? bpp/4 : 0, /* no alpha buffer */
+    static_cast<BYTE>(this->AlphaBitPlanes ? bpp/4 : 0), /* no alpha buffer */
     0,                              /* alpha bits (ignored) */
     0,                              /* no accumulation buffer */
     0, 0, 0, 0,                     /* accum bits (ignored) */
-    zbpp,                           /* depth buffer */
-    this->StencilCapable,           /* stencil buffer */
+    zbpp_byte,                      /* depth buffer */
+    static_cast<BYTE>(this->StencilCapable), /* stencil buffer */
     0,                              /* no auxiliary buffers */
     PFD_MAIN_PLANE,                 /* main layer */
     0,                              /* reserved */