package: use <pkg>_CONFIG_SCRIPTS wherever possible

Use the <pkg>_CONFIG_SCRIPTS mechanism in all packages for which it
does all what the package was doing. A few packages, like libxslt, are
for now left out, since they need some additional fixup (for example a
fixup of includedir).

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>