Add XBZRLE to ram_save_block and ram_save_live

Add XBZRLE to ram_save_block and ram_save_live

In the outgoing migration check to see if the page is cached and
changed, then send compressed page by using save_xbrle_page function.
In the incoming migration check to see if RAM_SAVE_FLAG_XBZRLE is set
and decompress the page (by using load_xbrle function).

Signed-off-by: Benoit Hudzia <[email protected]>
Signed-off-by: Petter Svard <[email protected]>
Signed-off-by: Aidan Shribman <[email protected]>
Signed-off-by: Orit Wasserman <[email protected]>
Reviewed-by: Luiz Capitulino <[email protected]>
Reviewed-by: Eric Blake <[email protected]>