I had the same problem, but if a did a new report it was all right, the new report was created and saved with the old schema:
xmlns="http://schemas.microsoft.com/sqlserver/reporting/2008/01/reportdefinition". (report viewed with a text editor)
When I added a parameters and re-saved, VS turned the schema in
new schema:
xmlns="http://schemas.microsoft.com/sqlserver/reporting/2016/01/reportdefinition"
But I found a solution that work also with Windows XP:
I install all necessary to manipulate the report with VS 2017 (in Visual studio 2017 are all external plug-in), then change the reference of my project e take 2 new referenze to this DLL:
1)
..\project\packages\Microsoft.ReportingServices.ReportViewerControl.Winforms.140.340.80\lib\net40\Microsoft.ReportViewer.WinForms.dll
2)
..\project\packages\Microsoft.ReportingServices.ReportViewerControl.Winforms.140.340.80\lib\net40\Microsoft.ReportViewer.Common.dll
After that all work.
This new version of DLL handle both "old schema" and "new schema"