mark again deps of pkgs in APT::Never-MarkAuto-Sections as manual

mark again deps of pkgs in APT::Never-MarkAuto-Sections as manual

In 50ef3344c3afaaf9943142906b2f976a0337d264 (and similar for other
branches), while 'fixing' the edgecase of a package being in multiple
sections (e.g. moved from libs to oldlibs in newer releases) I
accidently broke the feature itself completely by operating on the
package itself and no longer on its dependencies…

The behaviour isn't ideal in multiple ways, which we are hopefully able
to fix with new ideas as mentioned in the buglog, but until then the
functionality of this "hack" should be restored.

Reported-By: Raphaël Hertzog <hertzog@debian.org>
Tested-By: Adam Conrad <adconrad@ubuntu.com>
Closes: 793360
LP: 1479207
Thanks: Raphaël Hertzog and Adam Conrad for detailed reports and initial patches