windeployqt does not account for -qtnamespace option

If you've built your Qt using the -qtnamespace option, windeployqt will never find the correct platform plugin. 

It builds the filter as follows:

Debug: `qwindowsd.dll`

Release: `qwindows.dll`

When -qtnamespace has been used, the file will be called `qwindows_[namespace].dll` or `qwindows_[namespace]d.dll`

The fix should be to simply make the base filter `qwindows*` instead of `qwindows`. That way it will match on custom namespaces properly.