Add path package

For testing purposes we need to get the long path of filesystem paths
on Windows machines. By default non-UTF8 syscalls will return the short path
(Ex:"C:\PROGRA~1" instead of "C:\Program Files"). This package exports
previously private functions used in the symlink package to determine the
long path of a file/directory.
We need this because of the non-UTF8 syscalls. MkDir from the gocheck package is a good example of a short path as a return value, but the symlink syscalls that we do, are UTF8. We need to accurately compare the strings in our tests. A better alternative would be to propose a change in the gocheck package itself, but for the time being, this will be less disruptive.