Bug-fix release 2.5

1. bmaptool (or more precisely, the BmapCopy class) has an optimization where
   we switch to the "noop" I/O scheduler when writing directly to block
   devices. We also lessen the allowed amount of dirty data for this block
   device in order to create less memory pressure on the system. These tweaks
   are done by touching the corresponding sysfs files of the block device. The
   old bmaptool behavior was that it failed when it could not modify these
   files. However, there are systems where users can write to some block
   devices (USB sticks, for example), but they do not have permissions to
   change the sysfs files, and bmaptool did not work for normal users on such
   systems. In version 2.5 we change the behavior and do not fail anymore if we
   do not have enough permissions for changing sysfs files, simply because this
   is an optimization, although a quite important one. However, we do print a
   warning message.
2. Many improvements and fixes in the Debian packaging, which should make it
   simpler for distributions to package bmap-tools.