Update contrib/debian to latest Ubuntu PPA upload.

Update contrib/debian to latest Ubuntu PPA upload.

This:
 * Partially reverts 9f68ed6 (which fixed spelling in a changelog,
   though generally changelogs should be append-only).
 * Disables UPnP support (PPA has not had it for a while, and I
   still don't trust miniupnpc, plus it seems uneccessary - its
   been a while since we needed to care about Bitcoin-Qt home users
   getting their inbound ports auto-mapped).
 * Enables ZMQ.
 * Forces GUI to Qt4 to fix various issues people have been seeing
   on Ubuntu and elsewhere with Qt5.
 * Reverts 70899d70b (Bitcoin does not enable "instant payments",
   not is transaction management "carried out collectively by the
   network", for whatever "transaction management" means, finally
   Bitcoin Core is not the only way to use the Bitcoin currency,
   as seemingly implied in the description).