Install Dracut and initramfs-tools hooks unconditionally

Distribution packagers may ignore tools that are not relevant.
Add a mkinitcpio hook

Taken from the Arch Linux wiki, with some paths updated.
Untested.
Update the README to mention udev and initramfs hooks
Fix typo "Spcifies"
compile bcache-test

Add -lm option to compile bcache-test.

Signed-off-by: Akira Hayakawa <ruby.wktk@gmail.com>
Update ignored files
Accept -o for --data-offset

This was mentioned in the help but had been omitted.
Also accept flags with dashes

--data-offset didn't match the documentation.
Follow gnu style and accept dashes everywhere.
Correct typo in docs
udev: Skip floppies and cdroms
Take user-modified rules from /etc

Copy udev rules from /etc/udev/rules.d/ if they have been user-modified,
otherwise copy from /lib/udev/rules.d/ instead. Follows usual udev
conventions for modifying rules files.
Merge branch 'master' into debian

* master:
  Take user-modified rules from /etc
  udev: Skip floppies and cdroms
  Correct typo in docs
  Also accept flags with dashes
  Accept -o for --data-offset
  Update ignored files
  compile bcache-test
  Fix typo "Spcifies"
  Update the README to mention udev and initramfs hooks
  Add a mkinitcpio hook
  Install Dracut and initramfs-tools hooks unconditionally
Update standards version
Update debian changelog