Fix some windows build warnings

src/gui/qgssnaptogridcanvasitem.cpp

@@ -165,7 +165,7 @@ void QgsSnapToGridCanvasItem::updateZoomFactor()
     else
       mAvailableByZoomFactor = false;
   }
-  catch ( QgsCsException &e )
+  catch ( QgsCsException & )
   {
     // transform errors?
     // you've probably got worse problems than the grid with your digitizing operations in the current projection.

src/providers/wms/qgswmsprovider.cpp

@@ -483,7 +483,7 @@ void QgsWmsProvider::setQueryItem( QUrl &url, const QString &item, const QString
 {
   url.removeQueryItem( item );
   if ( value.isNull() )
-    url.addQueryItem( item, QStringLiteral( "" ) );  // skip-keyword-check
+    url.addQueryItem( item, "" );
   else
     url.addQueryItem( item, value );
 }