Bug#569989: xpi-pack: exclude changelog and license file from packed xpi

[Christoph Goehre]

Hi,

I've played around with my dispmua package and

  dh $@ --with xul-ext --buildsystem=xul_ext

in debian/rules. But I've hardly missed a 'autoexclude' for any
changelog or license file in the build root directory. So if I create
the new package, Lintian warn me about a extra-license-file and I find
another CHANGELOG copy in /usr/share/xul-ext/dispmua/CHANGELOG.

In the end, xpi-repack (introduced in debian/watch to create
orig.tar.gz) was totally useless for me and I need to use my own
debian/rules nonetheless.

Cheers,
Christoph