fhs: Use gzip compression for deb package

Ubuntu 14.04 defaults to xv which isn't supported by Ubuntu 10.10.
To restore compatibility, this patch explicitly sets the compression
format to gzip.

Target: trunk
Request: 2.9
Request: 2.8
Request: 2.7
Request: 2.6
Require-notes: no
Require-book: no
(cherry picked from commit 4b7d7a057f9fbbea32eeffb8caa741e62235c992)
Merge pull request #532 from gbehrmann/fix/2.6/rb6964

Fix/2.6/rb6964