Check for embedded copies of poppler/xpdf

The reported library name is poppler, as one can not use xpdf to stop
embedding the code.
Changelog entry for the previous commit
d/rules: Remove check-tag target

The target is replaced by "runtests" with "onlyrun=tag:<name-of-tag>"

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