Comment 7 for bug 576126

This patch should fix the encoding issue with the native Windows file save dialog.

It's a bit messy as we have to convert back and forth:
- Title from metadata in document properties is UTF8 encoded
- The file save dialog used Windows Unicode (UTF16)
- The target file is again UTF8 encoded

Please test if this works consistently.

On Windows 10 x64 with Inkscape 0.92.x r15396 this patch fixes the issue (system code page: ISO 8859-15, but should hopefully not matter)