
Bundling of vulkan-headers

The source includes debian/sync_headers.sh script, which is used
to bundle a matching version vulkan-headers. This makes sure that
the built library has a correct SONAME.

The procedure to update to a new upstream release goes usually like
this:

# git checkout upstream-unstable
# git merge <new upstream tag>
# git checkout debian-unstable
# git merge upstream-unstable
# dch -v <new version>
# debian/sync_headers.sh
# debian/rules gentarball
