dpkg 1.15.6 is slow as hell

[Sven Joachim <svenjoac@gmx.de>]

The decision to immediately fsync() all files written to disk has a
detrimental influence on dpkg's performance, especially when unpacking
large packages.  On my system which has a 2.5" hard disk with an ext4
filesystem, installing emacs23-common (containing 2123 files) with a hot
cache takes 76 seconds, almost all of which is spent during unpacking.
With dpkg 1.15.5.6, it takes 5.3 seconds, including processing three
triggers.  This is really painful. :-(

Sven