deb: add missing dependency on libhttp-date-perl

reported by James Robertson at
https://bugs.launchpad.net/ubuntu/+source/mythweb/+bug/1016780

(cherry picked from commit 06e718d9f1db894beabbbf4a1475835e45f6ff07)
deb: let mythtv-common suggest the debug symbols

This gives users backtraces that developers can make sense of on
the first crash. And hopefully helps with the automatic error
collector, too.
https://errors.ubuntu.com/?package=mythtv&period=month

Discussed at http://irc.mythtv.org/ircLog/channel/4/2013-08-23:17:10
17:10 until 19:22

(cherry picked from commit 160b29a11355864d413b2a201c023808ee750dd7)