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.
A checker that would use SameFile would be good in the cases that we have paths to existing files. We will write the checker and leave the PR open so that if we hit one of the other cases we can present a live test case. Do you think that this would be the proper way to proceed?