Make pan on windows work with fractional scaling

I've also done a lot of work on the wininstall script so it copies licence files and all the locale files from every required package, and creates a gtk3 settings file.

Fixed disappearing scrollbars and menu icons. I don't know where the gtk 3 team have got their ideas about user interface design from, but it has become very user unfriendly :-(

Also done a small fix to the windows link line as it was including the rc file twice

Fixes #144 (closed)