debian/changelog: merged additions from v1.8 branch

debian/changelog: merged additions from v1.8 branch
scripts/controllib.pl:
+ no need to have Origin in capit
+ consistently use &warn
+ fix -s to export all variables instead of just the first
scripts/dpkg-genchanges.pl: do not complain about missing packages if doing a source-only build
scripts/dpkg-buildpackage.sh:
+ correct filename for secret keyring in gpg test
+ fix -C
+ skip signing pause of building unsigned packages
+ improve srcmsg
+ test for invalid signinterface