Preserve the order of dependencies and build-dependencies

Preserve the order of dependencies and build-dependencies

* scripts/dpkg-gencontrol.pl, scripts/dpkg-source.pl:
Do not sort the dependency fields as order matters given
the greedy algorithm that APT uses when trying to resolve
dependencies. See discussion on debian-devel:
http://lists.debian.org/debian-devel/2008/02/msg00893.html
* man/dpkg-gencontrol.1: Document the above changes.

* scripts/Dpkg/Deps.pm (simplify_deps): Tries to respect order put
by the maintainer when simplifying dependencies.
* scripts/t/400_Dpkg_Deps.t: Add a test-case to ensure that
further changes respect this constraint.

* scripts/dpkg-shlibdeps.pl: Sort generated dependencies to
have a deterministic output.