default n-up printing of notes to sensible 2 x 1 not 1 x 2

i.e. throw away the maFirstPageSize cache based on the initial slide view which
is typically in landscape mode

So that if we change to notes which are usually in portrait mode, and then
visit n-up print, we get a default layout based on the notes orientation and
not the slides orientation.

I hate printing

Change-Id: I8b7b81ce1eec0f9c5ecd7509b311cf4026958c2c

vcl/source/window/printdlg.cxx

@@ -1787,6 +1787,14 @@ IMPL_LINK( PrintDialog, UIOption_SelectHdl, ListBox*, i_pBox )
         sal_Int32 nVal( i_pBox->GetSelectEntryPos() );
         pVal->Value <<= nVal;
 
+        //If we are in impress we start in print slides mode and get a
+        //maFirstPageSize for slides which are usually landscape mode, if we
+        //change to notes which are usually in portrait mode, and then visit
+        //n-up print, we will assume notes are in landscape unless we throw
+        //away maFirstPageSize when we change page content type
+        if (pVal->Name == "PageContentType")
+            maFirstPageSize = Size();
+
         checkOptionalControlDependencies();
 
         // update preview and page settings