dpkg-source: handle better symlinks to orig tarball

dpkg-source: handle better symlinks to orig tarball

* scripts/Dpkg/Path.pm (check_files_are_the_same): Add a new
parameter so that we can use stat() instead of lstat() and
compare if pointed files are the same.
* scripts/Dpkg/Source/Package.pm: Resolve symlinks before deciding
if both original tarballs are the same or not. Use the new
parameter of check_files_are_the_same() for this.
* scripts/Dpkg/Source/Package/V1_0.pm: Remove useless import of
check_files_are_the_same.