Upgrade gitian windows to qt-5.2.1

Please verify that your build matches this.
```27d005789086973fe3cad1a0fd840fa0596725e7503161f5a3322094e0b86925  qt-win32-5.2.1-gitian-r3.zip
4b824fde7345e13f69d20d3298c80ee100b2c2a9499ae1e4c6ac73f28f046bb8  qt-win64-5.2.1-gitian-r3.zip
```