Allow custom wxDataViewCtrl renderers to easily use attributes.

Set up the DC passed to wxDataViewCustomRenderer::Render() to use the font and
colour defined by the item attribute by default so that any calls to
RenderText() from it will use them automatically.

Also added public wxDataViewCustomRenderer::GetAttr() to allow retrieving the
attribute explicitly in Render().

The column using custom renderer in the dataview sample now works as expected
in the generic version; the native ones will be corrected in the upcoming
commits.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62590 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/carbon/dataview.cpp

@@ -1701,7 +1701,7 @@ wxMacDataViewDataBrowserListViewControl::DataBrowserDrawItemProc(DataBrowserItem
   {
       // make sure that 'Render' can draw only in the allowed area:
       dc->SetClippingRegion(content.left,content.top,content.right-content.left+1,content.bottom-content.top+1);
-      (void) (dataViewCustomRendererPtr->Render( cellrect, dc,
+      (void) (dataViewCustomRendererPtr->WXCallRender( cellrect, dc,
                                             ((state == kDataBrowserItemIsSelected) ? wxDATAVIEW_CELL_SELECTED : 0)));
       dc->DestroyClippingRegion(); // probably not necessary
   }