L::Util: Rewrite normalize_pkg_path to allow only one argument

Let normalize_pkg_path always normalize its first argument and let it
accept only one argument.  When receiving only one argument it behaves
more like Cwd::realpath rather than the current
"follow-symlink-and-normalize-result" behaviour.

Signed-off-by: Niels Thykier <niels@thykier.net>
c/shared-libs.pm: Remove make-shift abs_path function

Signed-off-by: Niels Thykier <niels@thykier.net>
c/{cruft,patch-systems}.pm: Remove some redundant imports

Signed-off-by: Niels Thykier <niels@thykier.net>