Rdiff-backup

Added --sleep-ratio option after hearing that rdiff-backup was too hard on hard disks (thanks to Steve Alexander for the suggestion).
Quick example: --sleep-ratio 0.25 makes rdiff-backup sleep about 25% of the time.
Maybe this will help on bandwidth usage also.

Fixed -m/--mirror-only option.

Added --exclude-other-filesystems option.
Thanks to Paul Wouters for the suggestion.

Added convenience field TotalDestinationSizeChange (total change in destination directory - mirror change + increments change) to session_statistics file.

Handle a particular situation better where a file changes in a certain way while rdiff-backup is processing it.
Before rdiff-backup would just crash;
now it skips the file.
Thanks to Scott Bender for the bug report.

A couple interface fixes to --remove-older-than.

Added some security features to the protocol, so rdiff-backup will now only allow commands from remote connections.
The extra security will be enabled automatically on the client (it knows what to expect), but the extra switches --restrict, --restrict-update-only, and --restrict-read-only have been added for use with --server.

Interface directly with librsync(.a|.so) instead of running "rdiff" command line utility.
This can significant save fork()ing time when processing lots of smallish files that have changed.
Also, rdiff is no longer required to be in the PATH.

Further speed optimizations, mostly reducing CPU consumption when scanning through unchanged files.

Fixed Path bug which could caused globbing and regexp include/exclude statements to malfunction when the base of the source directory was "/" (root of filesystem).
Thanks to Vlastimil Adamovsky for noting this bug.

Added quoting for spaces in directory_statistics file, hopefully making it easier to parse.

Fixed some bad C.
Besides being unportable and leaking memory, it may have lead to someone's backup directory getting deleted (?).

Tweaked some error recovery code to make it more like 0.8.0.

Improved the installation a bit.

Changed lots of the code to distribute as standard python package instead of single script.
Installation procedure is also different.

Speed optimizations - average user might see speed increase of 2 or more.

Added --null-separator argument so filenames can safely include newlines in an include/exclude filelist.

Fixed bug that affected restoring from current mirror with the '-r now' option.

Improved statistics support, and added --print-statistics and --calculate-average switches.
See the directory_statistics and session_statistics files in the rdiff-backup-data directory.

Major improvements to error correction and resuming.

Now signals SIGQUIT, SIGHUP, and SIGTERM are caught to exit more gracefully.

Fixed crankyness when --exclude-filelist is the last exclude option and it is given an empty file (thanks to Bryce C for report).