Bump version to 0.8.11

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Use fast xz compression with dracut

The run-time calculations are not as obvious as they seem. I mean I could
extend kexec to uncompress the image at load time, but that's not a clear
win. Total memory consumption is:

  initrd + decompression buffers + rootfs (uncompressed)

So, if compression can reduce the size of the initrd by more than the size
of decompression buffers, less memory is needed at runtime.

These are the numbes I get for a sample x86_64 kdump initrd:

rootfs size: 29331456
    (bigger than the uncompressed initrd because of page alignment)

                      initrd      total
uncompressed:       28373504   57704960
gzip-compressed:    11556846   40963478
xz-compressed (-0):  9696128   39289728
xz-compressed (-1):  9344168   39724200
xz-compressed (-2):  9205724   40634332
xz-compressed (-4):  8637964   42163724
xz-compressed (-6):  8357868   46077932
xz-compressed (-9):  8179820  104620140

Since "xz -0" has lower total memory requirements and is faster than
"gzip -9", let's use that.

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>