Handle ~/.vim in FollowSymlink

resolve() not understanding Windows mklink symlinks is a known bug[1],
so work around it and just keep track of known links to resolve. This is
ugly but effective.

[1]: https://code.google.com/p/vim/issues/detail?id=147
Add echo in vimscript

Similar to execute, you can echo a line or echo a selection. Useful for
checking if you're using the right arguments to has() or want to quickly
see a result.